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missing closing brach in /arch/arm/mach-sun4i/core.c #84

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simos opened this issue Oct 12, 2012 · 1 comment
Closed

missing closing brach in /arch/arm/mach-sun4i/core.c #84

simos opened this issue Oct 12, 2012 · 1 comment

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@simos
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simos commented Oct 12, 2012

Here is the description of the position.

diff --git a/arch/arm/mach-sun4i/core.c b/arch/arm/mach-sun4i/core.c
index 7f9cf88..999898b 100755
--- a/arch/arm/mach-sun4i/core.c
+++ b/arch/arm/mach-sun4i/core.c
@@ -149,6 +149,7 @@ static void __init sw_core_fixup(struct machine_desc *desc,
        if (size < 512) {
                pr_err("MALI: not enough memory to make reserve.\n");
                /* fallback to single bank will full size */
+               }
        else {
                mi->nr_banks = 1;
                mi->bank[0].start = 0x40000000;
@amery amery closed this as completed in 291aa80 Oct 12, 2012
@amery
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amery commented Oct 12, 2012

thank you

amery pushed a commit that referenced this issue Nov 12, 2013
Turn it into (for example):

[    0.073380] x86: Booting SMP configuration:
[    0.074005] .... node   #0, CPUs:          #1   #2   #3   #4   #5   #6   #7
[    0.603005] .... node   #1, CPUs:     #8   #9  #10  #11  #12  #13  #14  #15
[    1.200005] .... node   #2, CPUs:    #16  #17  #18  #19  #20  #21  #22  #23
[    1.796005] .... node   #3, CPUs:    #24  #25  #26  #27  #28  #29  #30  #31
[    2.393005] .... node   #4, CPUs:    #32  #33  #34  #35  #36  #37  #38  #39
[    2.996005] .... node   #5, CPUs:    #40  #41  #42  #43  #44  #45  #46  #47
[    3.600005] .... node   #6, CPUs:    #48  #49  #50  #51  #52  #53  #54  #55
[    4.202005] .... node   #7, CPUs:    #56  #57  #58  #59  #60  #61  #62  #63
[    4.811005] .... node   #8, CPUs:    #64  #65  #66  #67  #68  #69  #70  #71
[    5.421006] .... node   #9, CPUs:    #72  #73  #74  #75  #76  #77  #78  #79
[    6.032005] .... node  #10, CPUs:    #80  #81  #82  #83  #84  #85  #86  #87
[    6.648006] .... node  #11, CPUs:    #88  #89  #90  #91  #92  #93  #94  #95
[    7.262005] .... node  #12, CPUs:    #96  #97  #98  #99 #100 #101 #102 #103
[    7.865005] .... node  #13, CPUs:   #104 #105 #106 #107 #108 #109 #110 #111
[    8.466005] .... node  #14, CPUs:   #112 #113 #114 #115 #116 #117 #118 #119
[    9.073006] .... node  #15, CPUs:   #120 #121 #122 #123 #124 #125 #126 #127
[    9.679901] x86: Booted up 16 nodes, 128 CPUs

and drop useless elements.

Change num_digits() to hpa's division-avoiding, cell-phone-typed
version which he went at great lengths and pains to submit on a
Saturday evening.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: huawei.libin@huawei.com
Cc: wangyijing@huawei.com
Cc: fenghua.yu@intel.com
Cc: guohanjun@huawei.com
Cc: paul.gortmaker@windriver.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20130930095624.GB16383@pd.tnic
Signed-off-by: Ingo Molnar <mingo@kernel.org>
amery pushed a commit that referenced this issue Jul 25, 2016
Currently, smp_processor_id() is used to fetch the current CPU in
cpu_idle_loop(). Every time the idle thread runs, it fetches the
current CPU using smp_processor_id().

Since the idle thread is per CPU, the current CPU is constant, so we
can lift the load out of the loop, saving execution cycles/time in the
loop.

x86-64:

Before patch (execution in loop):
	148:    0f ae e8                lfence
	14b:    65 8b 04 25 00 00 00 00 mov %gs:0x0,%eax
	152:    00
	153:    89 c0                   mov %eax,%eax
	155:    49 0f a3 04 24          bt %rax,(%r12)

After patch (execution in loop):
	150:    0f ae e8                lfence
	153:    4d 0f a3 34 24          bt %r14,(%r12)

ARM64:

Before patch (execution in loop):
	168:    d5033d9f        dsb     ld
	16c:    b9405661        ldr     w1,[x19,#84]
	170:    1100fc20        add     w0,w1,#0x3f
	174:    6b1f003f        cmp     w1,wzr
	178:    1a81b000        csel    w0,w0,w1,lt
	17c:    130c7000        asr     w0,w0,#6
	180:    937d7c00        sbfiz   x0,x0,#3,#32
	184:    f8606aa0        ldr     x0,[x21,x0]
	188:    9ac12401        lsr     x1,x0,x1
	18c:    36000e61        tbz     w1,#0,358

After patch (execution in loop):
	1a8:    d50339df        dsb     ld
	1ac:    f8776ac0        ldr     x0,[x22,x23]
	ab0:    ea18001f        tst     x0,x24
	1b4:    54000ea0        b.eq    388

Further observance on ARM64 for 4 seconds shows that cpu_idle_loop is
called 8672 times. Shifting the code will save instructions executed
in loop and eventually time as well.

Signed-off-by: Gaurav Jindal <gaurav.jindal@spreadtrum.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Sanjeev Yadav <sanjeev.yadav@spreadtrum.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20160512101330.GA488@gauravjindalubtnb.del.spreadtrum.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
amery pushed a commit that referenced this issue May 4, 2017
Patch series "kasan: improve error reports", v2.

This patchset improves KASAN reports by making them easier to read and a
little more detailed.  Also improves mm/kasan/report.c readability.

Effectively changes a use-after-free report to:

  ==================================================================
  BUG: KASAN: use-after-free in kmalloc_uaf+0xaa/0xb6 [test_kasan]
  Write of size 1 at addr ffff88006aa59da8 by task insmod/3951

  CPU: 1 PID: 3951 Comm: insmod Tainted: G    B           4.10.0+ #84
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
  Call Trace:
   dump_stack+0x292/0x398
   print_address_description+0x73/0x280
   kasan_report.part.2+0x207/0x2f0
   __asan_report_store1_noabort+0x2c/0x30
   kmalloc_uaf+0xaa/0xb6 [test_kasan]
   kmalloc_tests_init+0x4f/0xa48 [test_kasan]
   do_one_initcall+0xf3/0x390
   do_init_module+0x215/0x5d0
   load_module+0x54de/0x82b0
   SYSC_init_module+0x3be/0x430
   SyS_init_module+0x9/0x10
   entry_SYSCALL_64_fastpath+0x1f/0xc2
  RIP: 0033:0x7f22cfd0b9da
  RSP: 002b:00007ffe69118a78 EFLAGS: 00000206 ORIG_RAX: 00000000000000af
  RAX: ffffffffffffffda RBX: 0000555671242090 RCX: 00007f22cfd0b9da
  RDX: 00007f22cffcaf88 RSI: 000000000004df7e RDI: 00007f22d0399000
  RBP: 00007f22cffcaf88 R08: 0000000000000003 R09: 0000000000000000
  R10: 00007f22cfd07d0a R11: 0000000000000206 R12: 0000555671243190
  R13: 000000000001fe81 R14: 0000000000000000 R15: 0000000000000004

  Allocated by task 3951:
   save_stack_trace+0x16/0x20
   save_stack+0x43/0xd0
   kasan_kmalloc+0xad/0xe0
   kmem_cache_alloc_trace+0x82/0x270
   kmalloc_uaf+0x56/0xb6 [test_kasan]
   kmalloc_tests_init+0x4f/0xa48 [test_kasan]
   do_one_initcall+0xf3/0x390
   do_init_module+0x215/0x5d0
   load_module+0x54de/0x82b0
   SYSC_init_module+0x3be/0x430
   SyS_init_module+0x9/0x10
   entry_SYSCALL_64_fastpath+0x1f/0xc2

  Freed by task 3951:
   save_stack_trace+0x16/0x20
   save_stack+0x43/0xd0
   kasan_slab_free+0x72/0xc0
   kfree+0xe8/0x2b0
   kmalloc_uaf+0x85/0xb6 [test_kasan]
   kmalloc_tests_init+0x4f/0xa48 [test_kasan]
   do_one_initcall+0xf3/0x390
   do_init_module+0x215/0x5d0
   load_module+0x54de/0x82b0
   SYSC_init_module+0x3be/0x430
   SyS_init_module+0x9/0x10
   entry_SYSCALL_64_fastpath+0x1f/0xc

  The buggy address belongs to the object at ffff88006aa59da0
   which belongs to the cache kmalloc-16 of size 16
  The buggy address is located 8 bytes inside of
   16-byte region [ffff88006aa59da0, ffff88006aa59db0)
  The buggy address belongs to the page:
  page:ffffea0001aa9640 count:1 mapcount:0 mapping:          (null) index:0x0
  flags: 0x100000000000100(slab)
  raw: 0100000000000100 0000000000000000 0000000000000000 0000000180800080
  raw: ffffea0001abe380 0000000700000007 ffff88006c401b40 0000000000000000
  page dumped because: kasan: bad access detected

  Memory state around the buggy address:
   ffff88006aa59c80: 00 00 fc fc 00 00 fc fc 00 00 fc fc 00 00 fc fc
   ffff88006aa59d00: 00 00 fc fc 00 00 fc fc 00 00 fc fc 00 00 fc fc
  >ffff88006aa59d80: fb fb fc fc fb fb fc fc fb fb fc fc fb fb fc fc
                                    ^
   ffff88006aa59e00: fb fb fc fc fb fb fc fc fb fb fc fc fb fb fc fc
   ffff88006aa59e80: fb fb fc fc 00 00 fc fc 00 00 fc fc 00 00 fc fc
  ==================================================================

from:

  ==================================================================
  BUG: KASAN: use-after-free in kmalloc_uaf+0xaa/0xb6 [test_kasan] at addr ffff88006c4dcb28
  Write of size 1 by task insmod/3984
  CPU: 1 PID: 3984 Comm: insmod Tainted: G    B           4.10.0+ #83
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
  Call Trace:
   dump_stack+0x292/0x398
   kasan_object_err+0x1c/0x70
   kasan_report.part.1+0x20e/0x4e0
   __asan_report_store1_noabort+0x2c/0x30
   kmalloc_uaf+0xaa/0xb6 [test_kasan]
   kmalloc_tests_init+0x4f/0xa48 [test_kasan]
   do_one_initcall+0xf3/0x390
   do_init_module+0x215/0x5d0
   load_module+0x54de/0x82b0
   SYSC_init_module+0x3be/0x430
   SyS_init_module+0x9/0x10
   entry_SYSCALL_64_fastpath+0x1f/0xc2
  RIP: 0033:0x7feca0f779da
  RSP: 002b:00007ffdfeae5218 EFLAGS: 00000206 ORIG_RAX: 00000000000000af
  RAX: ffffffffffffffda RBX: 000055a064c13090 RCX: 00007feca0f779da
  RDX: 00007feca1236f88 RSI: 000000000004df7e RDI: 00007feca1605000
  RBP: 00007feca1236f88 R08: 0000000000000003 R09: 0000000000000000
  R10: 00007feca0f73d0a R11: 0000000000000206 R12: 000055a064c14190
  R13: 000000000001fe81 R14: 0000000000000000 R15: 0000000000000004
  Object at ffff88006c4dcb20, in cache kmalloc-16 size: 16
  Allocated:
  PID = 3984
   save_stack_trace+0x16/0x20
   save_stack+0x43/0xd0
   kasan_kmalloc+0xad/0xe0
   kmem_cache_alloc_trace+0x82/0x270
   kmalloc_uaf+0x56/0xb6 [test_kasan]
   kmalloc_tests_init+0x4f/0xa48 [test_kasan]
   do_one_initcall+0xf3/0x390
   do_init_module+0x215/0x5d0
   load_module+0x54de/0x82b0
   SYSC_init_module+0x3be/0x430
   SyS_init_module+0x9/0x10
   entry_SYSCALL_64_fastpath+0x1f/0xc2
  Freed:
  PID = 3984
   save_stack_trace+0x16/0x20
   save_stack+0x43/0xd0
   kasan_slab_free+0x73/0xc0
   kfree+0xe8/0x2b0
   kmalloc_uaf+0x85/0xb6 [test_kasan]
   kmalloc_tests_init+0x4f/0xa48 [test_kasan]
   do_one_initcall+0xf3/0x390
   do_init_module+0x215/0x5d0
   load_module+0x54de/0x82b0
   SYSC_init_module+0x3be/0x430
   SyS_init_module+0x9/0x10
   entry_SYSCALL_64_fastpath+0x1f/0xc2
  Memory state around the buggy address:
   ffff88006c4dca00: fb fb fc fc fb fb fc fc fb fb fc fc fb fb fc fc
   ffff88006c4dca80: fb fb fc fc fb fb fc fc fb fb fc fc fb fb fc fc
  >ffff88006c4dcb00: fb fb fc fc fb fb fc fc fb fb fc fc fb fb fc fc
                                    ^
   ffff88006c4dcb80: fb fb fc fc 00 00 fc fc fb fb fc fc fb fb fc fc
   ffff88006c4dcc00: fb fb fc fc fb fb fc fc fb fb fc fc fb fb fc fc
  ==================================================================

This patch (of 9):

Introduce get_shadow_bug_type() function, which determines bug type
based on the shadow value for a particular kernel address.  Introduce
get_wild_bug_type() function, which determines bug type for addresses
which don't have a corresponding shadow value.

Link: http://lkml.kernel.org/r/20170302134851.101218-2-andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
amery pushed a commit that referenced this issue Jul 4, 2017
With the enhanced CPU hotplug lockdep coverage the following lockdep splat
happens:

======================================================
WARNING: possible circular locking dependency detected
4.12.0-rc2+ #84 Tainted: G        W      
------------------------------------------------------
cpuhp/1/15 is trying to acquire lock:
flush_work+0x39/0x2f0

but task is already holding lock:
cpuhp_thread_fun+0x30/0x160

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #2 (cpuhp_state){+.+.+.}:
       lock_acquire+0xb4/0x200
       cpuhp_kick_ap_work+0x72/0x330
       _cpu_down+0x8b/0x100
       do_cpu_down+0x3e/0x60
       cpu_down+0x10/0x20
       cpu_subsys_offline+0x14/0x20
       device_offline+0x88/0xb0
       online_store+0x4c/0xa0
       dev_attr_store+0x18/0x30
       sysfs_kf_write+0x45/0x60
       kernfs_fop_write+0x156/0x1e0
       __vfs_write+0x37/0x160
       vfs_write+0xca/0x1c0
       SyS_write+0x58/0xc0
       entry_SYSCALL_64_fastpath+0x23/0xc2

-> #1 (cpu_hotplug_lock.rw_sem){++++++}:
       lock_acquire+0xb4/0x200
       cpus_read_lock+0x3d/0xb0
       apply_workqueue_attrs+0x17/0x50
       __alloc_workqueue_key+0x1e1/0x530
       scsi_host_alloc+0x373/0x480 [scsi_mod]
       ata_scsi_add_hosts+0xcb/0x130 [libata]
       ata_host_register+0x11a/0x2c0 [libata]
       ata_host_activate+0xf0/0x150 [libata]
       ahci_host_activate+0x13e/0x170 [libahci]
       ahci_init_one+0xa3a/0xd3f [ahci]
       local_pci_probe+0x45/0xa0
       work_for_cpu_fn+0x14/0x20
       process_one_work+0x1f9/0x690
       worker_thread+0x200/0x3d0
       kthread+0x138/0x170
       ret_from_fork+0x31/0x40

-> #0 ((&wfc.work)){+.+.+.}:
       __lock_acquire+0x11e1/0x13e0
       lock_acquire+0xb4/0x200
       flush_work+0x5c/0x2f0
       work_on_cpu+0xa1/0xd0
       acpi_processor_get_throttling+0x3d/0x50
       acpi_processor_reevaluate_tstate+0x2c/0x50
       acpi_soft_cpu_online+0x69/0xd0
       cpuhp_invoke_callback+0xb4/0x8b0
       cpuhp_up_callbacks+0x36/0xc0
       cpuhp_thread_fun+0x14e/0x160
       smpboot_thread_fn+0x1e8/0x300
       kthread+0x138/0x170
       ret_from_fork+0x31/0x40

other info that might help us debug this:

Chain exists of:
  (&wfc.work) --> cpu_hotplug_lock.rw_sem --> cpuhp_state

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(cpuhp_state);
                               lock(cpu_hotplug_lock.rw_sem);
                               lock(cpuhp_state);
  lock((&wfc.work));

 *** DEADLOCK ***

1 lock held by cpuhp/1/15:
cpuhp_thread_fun+0x30/0x160

stack backtrace:
CPU: 1 PID: 15 Comm: cpuhp/1 Tainted: G        W       4.12.0-rc2+ #84
Hardware name: Supermicro SYS-4048B-TR4FT/X10QBi, BIOS 1.1a 07/29/2015
Call Trace:
 dump_stack+0x85/0xc4
 print_circular_bug+0x209/0x217
 __lock_acquire+0x11e1/0x13e0
 lock_acquire+0xb4/0x200
 ? lock_acquire+0xb4/0x200
 ? flush_work+0x39/0x2f0
 ? acpi_processor_start+0x50/0x50
 flush_work+0x5c/0x2f0
 ? flush_work+0x39/0x2f0
 ? acpi_processor_start+0x50/0x50
 ? mark_held_locks+0x6d/0x90
 ? queue_work_on+0x56/0x90
 ? trace_hardirqs_on_caller+0x154/0x1c0
 ? trace_hardirqs_on+0xd/0x10
 ? acpi_processor_start+0x50/0x50
 work_on_cpu+0xa1/0xd0
 ? find_worker_executing_work+0x50/0x50
 ? acpi_processor_power_exit+0x70/0x70
 acpi_processor_get_throttling+0x3d/0x50
 acpi_processor_reevaluate_tstate+0x2c/0x50
 acpi_soft_cpu_online+0x69/0xd0
 cpuhp_invoke_callback+0xb4/0x8b0
 ? lock_acquire+0xb4/0x200
 ? padata_replace+0x120/0x120
 cpuhp_up_callbacks+0x36/0xc0
 cpuhp_thread_fun+0x14e/0x160
 smpboot_thread_fn+0x1e8/0x300
 kthread+0x138/0x170
 ? sort_range+0x30/0x30
 ? kthread_create_on_node+0x70/0x70
 ret_from_fork+0x31/0x40

The problem is that the work is scheduled on the current CPU from the
hotplug thread associated with that CPU.

It's not required to invoke these functions via the workqueue because the
hotplug thread runs on the target CPU already.

Check whether current is a per cpu thread pinned on the target CPU and
invoke the function directly to avoid the workqueue.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-acpi@vger.kernel.org
Cc: Len Brown <lenb@kernel.org>
Link: http://lkml.kernel.org/r/20170524081549.620489733@linutronix.de
jwrdegoede pushed a commit to jwrdegoede/linux-sunxi that referenced this issue Dec 24, 2018
This is the much more correct fix for my earlier attempt at:

https://lkml.org/lkml/2018/12/10/118

Short recap:

- There's not actually a locking issue, it's just lockdep being a bit
  too eager to complain about a possible deadlock.

- Contrary to what I claimed the real problem is recursion on
  kn->count. Greg pointed me at sysfs_break_active_protection(), used
  by the scsi subsystem to allow a sysfs file to unbind itself. That
  would be a real deadlock, which isn't what's happening here. Also,
  breaking the active protection means we'd need to manually handle
  all the lifetime fun.

- With Rafael we discussed the task_work approach, which kinda works,
  but has two downsides: It's a functional change for a lockdep
  annotation issue, and it won't work for the bind file (which needs
  to get the errno from the driver load function back to userspace).

- Greg also asked why this never showed up: To hit this you need to
  unregister a 2nd driver from the unload code of your first driver. I
  guess only gpus do that. The bug has always been there, but only
  with a recent patch series did we add more locks so that lockdep
  built a chain from unbinding the snd-hda driver to the
  acpi_video_unregister call.

Full lockdep splat:

[12301.898799] ============================================
[12301.898805] WARNING: possible recursive locking detected
[12301.898811] 4.20.0-rc7+ linux-sunxi#84 Not tainted
[12301.898815] --------------------------------------------
[12301.898821] bash/5297 is trying to acquire lock:
[12301.898826] 00000000f61c6093 (kn->count#39){++++}, at: kernfs_remove_by_name_ns+0x3b/0x80
[12301.898841] but task is already holding lock:
[12301.898847] 000000005f634021 (kn->count#39){++++}, at: kernfs_fop_write+0xdc/0x190
[12301.898856] other info that might help us debug this:
[12301.898862]  Possible unsafe locking scenario:
[12301.898867]        CPU0
[12301.898870]        ----
[12301.898874]   lock(kn->count#39);
[12301.898879]   lock(kn->count#39);
[12301.898883] *** DEADLOCK ***
[12301.898891]  May be due to missing lock nesting notation
[12301.898899] 5 locks held by bash/5297:
[12301.898903]  #0: 00000000cd800e54 (sb_writers#4){.+.+}, at: vfs_write+0x17f/0x1b0
[12301.898915]  #1: 000000000465e7c2 (&of->mutex){+.+.}, at: kernfs_fop_write+0xd3/0x190
[12301.898925]  #2: 000000005f634021 (kn->count#39){++++}, at: kernfs_fop_write+0xdc/0x190
[12301.898936]  #3: 00000000414ef7ac (&dev->mutex){....}, at: device_release_driver_internal+0x34/0x240
[12301.898950]  #4: 000000003218fbdf (register_count_mutex){+.+.}, at: acpi_video_unregister+0xe/0x40
[12301.898960] stack backtrace:
[12301.898968] CPU: 1 PID: 5297 Comm: bash Not tainted 4.20.0-rc7+ linux-sunxi#84
[12301.898974] Hardware name: Hewlett-Packard HP EliteBook 8460p/161C, BIOS 68SCF Ver. F.01 03/11/2011
[12301.898982] Call Trace:
[12301.898989]  dump_stack+0x67/0x9b
[12301.898997]  __lock_acquire+0x6ad/0x1410
[12301.899003]  ? kernfs_remove_by_name_ns+0x3b/0x80
[12301.899010]  ? find_held_lock+0x2d/0x90
[12301.899017]  ? mutex_spin_on_owner+0xe4/0x150
[12301.899023]  ? find_held_lock+0x2d/0x90
[12301.899030]  ? lock_acquire+0x90/0x180
[12301.899036]  lock_acquire+0x90/0x180
[12301.899042]  ? kernfs_remove_by_name_ns+0x3b/0x80
[12301.899049]  __kernfs_remove+0x296/0x310
[12301.899055]  ? kernfs_remove_by_name_ns+0x3b/0x80
[12301.899060]  ? kernfs_name_hash+0xd/0x80
[12301.899066]  ? kernfs_find_ns+0x6c/0x100
[12301.899073]  kernfs_remove_by_name_ns+0x3b/0x80
[12301.899080]  bus_remove_driver+0x92/0xa0
[12301.899085]  acpi_video_unregister+0x24/0x40
[12301.899127]  i915_driver_unload+0x42/0x130 [i915]
[12301.899160]  i915_pci_remove+0x19/0x30 [i915]
[12301.899169]  pci_device_remove+0x36/0xb0
[12301.899176]  device_release_driver_internal+0x185/0x240
[12301.899183]  unbind_store+0xaf/0x180
[12301.899189]  kernfs_fop_write+0x104/0x190
[12301.899195]  __vfs_write+0x31/0x180
[12301.899203]  ? rcu_read_lock_sched_held+0x6f/0x80
[12301.899209]  ? rcu_sync_lockdep_assert+0x29/0x50
[12301.899216]  ? __sb_start_write+0x13c/0x1a0
[12301.899221]  ? vfs_write+0x17f/0x1b0
[12301.899227]  vfs_write+0xb9/0x1b0
[12301.899233]  ksys_write+0x50/0xc0
[12301.899239]  do_syscall_64+0x4b/0x180
[12301.899247]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
[12301.899253] RIP: 0033:0x7f452ac7f7a4
[12301.899259] Code: 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 80 00 00 00 00 8b 05 aa f0 2c 00 48 63 ff 85 c0 75 13 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 54 f3 c3 66 90 55 53 48 89 d5 48 89 f3 48 83
[12301.899273] RSP: 002b:00007ffceafa6918 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
[12301.899282] RAX: ffffffffffffffda RBX: 000000000000000d RCX: 00007f452ac7f7a4
[12301.899288] RDX: 000000000000000d RSI: 00005612a1abf7c0 RDI: 0000000000000001
[12301.899295] RBP: 00005612a1abf7c0 R08: 000000000000000a R09: 00005612a1c46730
[12301.899301] R10: 000000000000000a R11: 0000000000000246 R12: 000000000000000d
[12301.899308] R13: 0000000000000001 R14: 00007f452af4a740 R15: 000000000000000d

Locking around I've noticed that usb and i2c already handle similar
recursion problems, where a sysfs file can unbind the same type of
sysfs somewhere else in the hierarchy. Relevant commits are:

commit 356c05d
Author: Alan Stern <stern@rowland.harvard.edu>
Date:   Mon May 14 13:30:03 2012 -0400

    sysfs: get rid of some lockdep false positives

commit e9b526f
Author: Alexander Sverdlin <alexander.sverdlin@nsn.com>
Date:   Fri May 17 14:56:35 2013 +0200

    i2c: suppress lockdep warning on delete_device

Implement the same trick for driver bind/unbind.

v2: Put the macro into bus.c (Greg).

Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ramalingam C <ramalingam.c@intel.com>
Cc: Arend van Spriel <aspriel@gmail.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Bartosz Golaszewski <brgl@bgdev.pl>
Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Cc: Vivek Gautam <vivek.gautam@codeaurora.org>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>

Note that Greg already merged this, so this should drop out as soon as
we've moved forward past 4.21-rc1.
-Daniel
amery pushed a commit that referenced this issue Dec 29, 2018
This is the much more correct fix for my earlier attempt at:

https://lkml.org/lkml/2018/12/10/118

Short recap:

- There's not actually a locking issue, it's just lockdep being a bit
  too eager to complain about a possible deadlock.

- Contrary to what I claimed the real problem is recursion on
  kn->count. Greg pointed me at sysfs_break_active_protection(), used
  by the scsi subsystem to allow a sysfs file to unbind itself. That
  would be a real deadlock, which isn't what's happening here. Also,
  breaking the active protection means we'd need to manually handle
  all the lifetime fun.

- With Rafael we discussed the task_work approach, which kinda works,
  but has two downsides: It's a functional change for a lockdep
  annotation issue, and it won't work for the bind file (which needs
  to get the errno from the driver load function back to userspace).

- Greg also asked why this never showed up: To hit this you need to
  unregister a 2nd driver from the unload code of your first driver. I
  guess only gpus do that. The bug has always been there, but only
  with a recent patch series did we add more locks so that lockdep
  built a chain from unbinding the snd-hda driver to the
  acpi_video_unregister call.

Full lockdep splat:

[12301.898799] ============================================
[12301.898805] WARNING: possible recursive locking detected
[12301.898811] 4.20.0-rc7+ #84 Not tainted
[12301.898815] --------------------------------------------
[12301.898821] bash/5297 is trying to acquire lock:
[12301.898826] 00000000f61c6093 (kn->count#39){++++}, at: kernfs_remove_by_name_ns+0x3b/0x80
[12301.898841] but task is already holding lock:
[12301.898847] 000000005f634021 (kn->count#39){++++}, at: kernfs_fop_write+0xdc/0x190
[12301.898856] other info that might help us debug this:
[12301.898862]  Possible unsafe locking scenario:
[12301.898867]        CPU0
[12301.898870]        ----
[12301.898874]   lock(kn->count#39);
[12301.898879]   lock(kn->count#39);
[12301.898883] *** DEADLOCK ***
[12301.898891]  May be due to missing lock nesting notation
[12301.898899] 5 locks held by bash/5297:
[12301.898903]  #0: 00000000cd800e54 (sb_writers#4){.+.+}, at: vfs_write+0x17f/0x1b0
[12301.898915]  #1: 000000000465e7c2 (&of->mutex){+.+.}, at: kernfs_fop_write+0xd3/0x190
[12301.898925]  #2: 000000005f634021 (kn->count#39){++++}, at: kernfs_fop_write+0xdc/0x190
[12301.898936]  #3: 00000000414ef7ac (&dev->mutex){....}, at: device_release_driver_internal+0x34/0x240
[12301.898950]  #4: 000000003218fbdf (register_count_mutex){+.+.}, at: acpi_video_unregister+0xe/0x40
[12301.898960] stack backtrace:
[12301.898968] CPU: 1 PID: 5297 Comm: bash Not tainted 4.20.0-rc7+ #84
[12301.898974] Hardware name: Hewlett-Packard HP EliteBook 8460p/161C, BIOS 68SCF Ver. F.01 03/11/2011
[12301.898982] Call Trace:
[12301.898989]  dump_stack+0x67/0x9b
[12301.898997]  __lock_acquire+0x6ad/0x1410
[12301.899003]  ? kernfs_remove_by_name_ns+0x3b/0x80
[12301.899010]  ? find_held_lock+0x2d/0x90
[12301.899017]  ? mutex_spin_on_owner+0xe4/0x150
[12301.899023]  ? find_held_lock+0x2d/0x90
[12301.899030]  ? lock_acquire+0x90/0x180
[12301.899036]  lock_acquire+0x90/0x180
[12301.899042]  ? kernfs_remove_by_name_ns+0x3b/0x80
[12301.899049]  __kernfs_remove+0x296/0x310
[12301.899055]  ? kernfs_remove_by_name_ns+0x3b/0x80
[12301.899060]  ? kernfs_name_hash+0xd/0x80
[12301.899066]  ? kernfs_find_ns+0x6c/0x100
[12301.899073]  kernfs_remove_by_name_ns+0x3b/0x80
[12301.899080]  bus_remove_driver+0x92/0xa0
[12301.899085]  acpi_video_unregister+0x24/0x40
[12301.899127]  i915_driver_unload+0x42/0x130 [i915]
[12301.899160]  i915_pci_remove+0x19/0x30 [i915]
[12301.899169]  pci_device_remove+0x36/0xb0
[12301.899176]  device_release_driver_internal+0x185/0x240
[12301.899183]  unbind_store+0xaf/0x180
[12301.899189]  kernfs_fop_write+0x104/0x190
[12301.899195]  __vfs_write+0x31/0x180
[12301.899203]  ? rcu_read_lock_sched_held+0x6f/0x80
[12301.899209]  ? rcu_sync_lockdep_assert+0x29/0x50
[12301.899216]  ? __sb_start_write+0x13c/0x1a0
[12301.899221]  ? vfs_write+0x17f/0x1b0
[12301.899227]  vfs_write+0xb9/0x1b0
[12301.899233]  ksys_write+0x50/0xc0
[12301.899239]  do_syscall_64+0x4b/0x180
[12301.899247]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
[12301.899253] RIP: 0033:0x7f452ac7f7a4
[12301.899259] Code: 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 80 00 00 00 00 8b 05 aa f0 2c 00 48 63 ff 85 c0 75 13 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 54 f3 c3 66 90 55 53 48 89 d5 48 89 f3 48 83
[12301.899273] RSP: 002b:00007ffceafa6918 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
[12301.899282] RAX: ffffffffffffffda RBX: 000000000000000d RCX: 00007f452ac7f7a4
[12301.899288] RDX: 000000000000000d RSI: 00005612a1abf7c0 RDI: 0000000000000001
[12301.899295] RBP: 00005612a1abf7c0 R08: 000000000000000a R09: 00005612a1c46730
[12301.899301] R10: 000000000000000a R11: 0000000000000246 R12: 000000000000000d
[12301.899308] R13: 0000000000000001 R14: 00007f452af4a740 R15: 000000000000000d

Looking around I've noticed that usb and i2c already handle similar
recursion problems, where a sysfs file can unbind the same type of
sysfs somewhere else in the hierarchy. Relevant commits are:

commit 356c05d
Author: Alan Stern <stern@rowland.harvard.edu>
Date:   Mon May 14 13:30:03 2012 -0400

    sysfs: get rid of some lockdep false positives

commit e9b526f
Author: Alexander Sverdlin <alexander.sverdlin@nsn.com>
Date:   Fri May 17 14:56:35 2013 +0200

    i2c: suppress lockdep warning on delete_device

Implement the same trick for driver bind/unbind.

v2: Put the macro into bus.c (Greg).

Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Ramalingam C <ramalingam.c@intel.com>
Cc: Arend van Spriel <aspriel@gmail.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Bartosz Golaszewski <brgl@bgdev.pl>
Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Cc: Vivek Gautam <vivek.gautam@codeaurora.org>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
repojohnray pushed a commit to repojohnray/linux-sunxi-4.7.y that referenced this issue Jan 26, 2019
[ Upstream commit 4f4b374 ]

This is the much more correct fix for my earlier attempt at:

https://lkml.org/lkml/2018/12/10/118

Short recap:

- There's not actually a locking issue, it's just lockdep being a bit
  too eager to complain about a possible deadlock.

- Contrary to what I claimed the real problem is recursion on
  kn->count. Greg pointed me at sysfs_break_active_protection(), used
  by the scsi subsystem to allow a sysfs file to unbind itself. That
  would be a real deadlock, which isn't what's happening here. Also,
  breaking the active protection means we'd need to manually handle
  all the lifetime fun.

- With Rafael we discussed the task_work approach, which kinda works,
  but has two downsides: It's a functional change for a lockdep
  annotation issue, and it won't work for the bind file (which needs
  to get the errno from the driver load function back to userspace).

- Greg also asked why this never showed up: To hit this you need to
  unregister a 2nd driver from the unload code of your first driver. I
  guess only gpus do that. The bug has always been there, but only
  with a recent patch series did we add more locks so that lockdep
  built a chain from unbinding the snd-hda driver to the
  acpi_video_unregister call.

Full lockdep splat:

[12301.898799] ============================================
[12301.898805] WARNING: possible recursive locking detected
[12301.898811] 4.20.0-rc7+ linux-sunxi#84 Not tainted
[12301.898815] --------------------------------------------
[12301.898821] bash/5297 is trying to acquire lock:
[12301.898826] 00000000f61c6093 (kn->count#39){++++}, at: kernfs_remove_by_name_ns+0x3b/0x80
[12301.898841] but task is already holding lock:
[12301.898847] 000000005f634021 (kn->count#39){++++}, at: kernfs_fop_write+0xdc/0x190
[12301.898856] other info that might help us debug this:
[12301.898862]  Possible unsafe locking scenario:
[12301.898867]        CPU0
[12301.898870]        ----
[12301.898874]   lock(kn->count#39);
[12301.898879]   lock(kn->count#39);
[12301.898883] *** DEADLOCK ***
[12301.898891]  May be due to missing lock nesting notation
[12301.898899] 5 locks held by bash/5297:
[12301.898903]  #0: 00000000cd800e54 (sb_writers#4){.+.+}, at: vfs_write+0x17f/0x1b0
[12301.898915]  jwrdegoede#1: 000000000465e7c2 (&of->mutex){+.+.}, at: kernfs_fop_write+0xd3/0x190
[12301.898925]  jwrdegoede#2: 000000005f634021 (kn->count#39){++++}, at: kernfs_fop_write+0xdc/0x190
[12301.898936]  jwrdegoede#3: 00000000414ef7ac (&dev->mutex){....}, at: device_release_driver_internal+0x34/0x240
[12301.898950]  jwrdegoede#4: 000000003218fbdf (register_count_mutex){+.+.}, at: acpi_video_unregister+0xe/0x40
[12301.898960] stack backtrace:
[12301.898968] CPU: 1 PID: 5297 Comm: bash Not tainted 4.20.0-rc7+ linux-sunxi#84
[12301.898974] Hardware name: Hewlett-Packard HP EliteBook 8460p/161C, BIOS 68SCF Ver. F.01 03/11/2011
[12301.898982] Call Trace:
[12301.898989]  dump_stack+0x67/0x9b
[12301.898997]  __lock_acquire+0x6ad/0x1410
[12301.899003]  ? kernfs_remove_by_name_ns+0x3b/0x80
[12301.899010]  ? find_held_lock+0x2d/0x90
[12301.899017]  ? mutex_spin_on_owner+0xe4/0x150
[12301.899023]  ? find_held_lock+0x2d/0x90
[12301.899030]  ? lock_acquire+0x90/0x180
[12301.899036]  lock_acquire+0x90/0x180
[12301.899042]  ? kernfs_remove_by_name_ns+0x3b/0x80
[12301.899049]  __kernfs_remove+0x296/0x310
[12301.899055]  ? kernfs_remove_by_name_ns+0x3b/0x80
[12301.899060]  ? kernfs_name_hash+0xd/0x80
[12301.899066]  ? kernfs_find_ns+0x6c/0x100
[12301.899073]  kernfs_remove_by_name_ns+0x3b/0x80
[12301.899080]  bus_remove_driver+0x92/0xa0
[12301.899085]  acpi_video_unregister+0x24/0x40
[12301.899127]  i915_driver_unload+0x42/0x130 [i915]
[12301.899160]  i915_pci_remove+0x19/0x30 [i915]
[12301.899169]  pci_device_remove+0x36/0xb0
[12301.899176]  device_release_driver_internal+0x185/0x240
[12301.899183]  unbind_store+0xaf/0x180
[12301.899189]  kernfs_fop_write+0x104/0x190
[12301.899195]  __vfs_write+0x31/0x180
[12301.899203]  ? rcu_read_lock_sched_held+0x6f/0x80
[12301.899209]  ? rcu_sync_lockdep_assert+0x29/0x50
[12301.899216]  ? __sb_start_write+0x13c/0x1a0
[12301.899221]  ? vfs_write+0x17f/0x1b0
[12301.899227]  vfs_write+0xb9/0x1b0
[12301.899233]  ksys_write+0x50/0xc0
[12301.899239]  do_syscall_64+0x4b/0x180
[12301.899247]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
[12301.899253] RIP: 0033:0x7f452ac7f7a4
[12301.899259] Code: 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 80 00 00 00 00 8b 05 aa f0 2c 00 48 63 ff 85 c0 75 13 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 54 f3 c3 66 90 55 53 48 89 d5 48 89 f3 48 83
[12301.899273] RSP: 002b:00007ffceafa6918 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
[12301.899282] RAX: ffffffffffffffda RBX: 000000000000000d RCX: 00007f452ac7f7a4
[12301.899288] RDX: 000000000000000d RSI: 00005612a1abf7c0 RDI: 0000000000000001
[12301.899295] RBP: 00005612a1abf7c0 R08: 000000000000000a R09: 00005612a1c46730
[12301.899301] R10: 000000000000000a R11: 0000000000000246 R12: 000000000000000d
[12301.899308] R13: 0000000000000001 R14: 00007f452af4a740 R15: 000000000000000d

Looking around I've noticed that usb and i2c already handle similar
recursion problems, where a sysfs file can unbind the same type of
sysfs somewhere else in the hierarchy. Relevant commits are:

commit 356c05d
Author: Alan Stern <stern@rowland.harvard.edu>
Date:   Mon May 14 13:30:03 2012 -0400

    sysfs: get rid of some lockdep false positives

commit e9b526f
Author: Alexander Sverdlin <alexander.sverdlin@nsn.com>
Date:   Fri May 17 14:56:35 2013 +0200

    i2c: suppress lockdep warning on delete_device

Implement the same trick for driver bind/unbind.

v2: Put the macro into bus.c (Greg).

Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Ramalingam C <ramalingam.c@intel.com>
Cc: Arend van Spriel <aspriel@gmail.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Bartosz Golaszewski <brgl@bgdev.pl>
Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Cc: Vivek Gautam <vivek.gautam@codeaurora.org>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
repojohnray pushed a commit to repojohnray/linux-sunxi-4.7.y that referenced this issue Jan 26, 2019
[ Upstream commit 4f4b374 ]

This is the much more correct fix for my earlier attempt at:

https://lkml.org/lkml/2018/12/10/118

Short recap:

- There's not actually a locking issue, it's just lockdep being a bit
  too eager to complain about a possible deadlock.

- Contrary to what I claimed the real problem is recursion on
  kn->count. Greg pointed me at sysfs_break_active_protection(), used
  by the scsi subsystem to allow a sysfs file to unbind itself. That
  would be a real deadlock, which isn't what's happening here. Also,
  breaking the active protection means we'd need to manually handle
  all the lifetime fun.

- With Rafael we discussed the task_work approach, which kinda works,
  but has two downsides: It's a functional change for a lockdep
  annotation issue, and it won't work for the bind file (which needs
  to get the errno from the driver load function back to userspace).

- Greg also asked why this never showed up: To hit this you need to
  unregister a 2nd driver from the unload code of your first driver. I
  guess only gpus do that. The bug has always been there, but only
  with a recent patch series did we add more locks so that lockdep
  built a chain from unbinding the snd-hda driver to the
  acpi_video_unregister call.

Full lockdep splat:

[12301.898799] ============================================
[12301.898805] WARNING: possible recursive locking detected
[12301.898811] 4.20.0-rc7+ linux-sunxi#84 Not tainted
[12301.898815] --------------------------------------------
[12301.898821] bash/5297 is trying to acquire lock:
[12301.898826] 00000000f61c6093 (kn->count#39){++++}, at: kernfs_remove_by_name_ns+0x3b/0x80
[12301.898841] but task is already holding lock:
[12301.898847] 000000005f634021 (kn->count#39){++++}, at: kernfs_fop_write+0xdc/0x190
[12301.898856] other info that might help us debug this:
[12301.898862]  Possible unsafe locking scenario:
[12301.898867]        CPU0
[12301.898870]        ----
[12301.898874]   lock(kn->count#39);
[12301.898879]   lock(kn->count#39);
[12301.898883] *** DEADLOCK ***
[12301.898891]  May be due to missing lock nesting notation
[12301.898899] 5 locks held by bash/5297:
[12301.898903]  #0: 00000000cd800e54 (sb_writers#4){.+.+}, at: vfs_write+0x17f/0x1b0
[12301.898915]  jwrdegoede#1: 000000000465e7c2 (&of->mutex){+.+.}, at: kernfs_fop_write+0xd3/0x190
[12301.898925]  jwrdegoede#2: 000000005f634021 (kn->count#39){++++}, at: kernfs_fop_write+0xdc/0x190
[12301.898936]  jwrdegoede#3: 00000000414ef7ac (&dev->mutex){....}, at: device_release_driver_internal+0x34/0x240
[12301.898950]  jwrdegoede#4: 000000003218fbdf (register_count_mutex){+.+.}, at: acpi_video_unregister+0xe/0x40
[12301.898960] stack backtrace:
[12301.898968] CPU: 1 PID: 5297 Comm: bash Not tainted 4.20.0-rc7+ linux-sunxi#84
[12301.898974] Hardware name: Hewlett-Packard HP EliteBook 8460p/161C, BIOS 68SCF Ver. F.01 03/11/2011
[12301.898982] Call Trace:
[12301.898989]  dump_stack+0x67/0x9b
[12301.898997]  __lock_acquire+0x6ad/0x1410
[12301.899003]  ? kernfs_remove_by_name_ns+0x3b/0x80
[12301.899010]  ? find_held_lock+0x2d/0x90
[12301.899017]  ? mutex_spin_on_owner+0xe4/0x150
[12301.899023]  ? find_held_lock+0x2d/0x90
[12301.899030]  ? lock_acquire+0x90/0x180
[12301.899036]  lock_acquire+0x90/0x180
[12301.899042]  ? kernfs_remove_by_name_ns+0x3b/0x80
[12301.899049]  __kernfs_remove+0x296/0x310
[12301.899055]  ? kernfs_remove_by_name_ns+0x3b/0x80
[12301.899060]  ? kernfs_name_hash+0xd/0x80
[12301.899066]  ? kernfs_find_ns+0x6c/0x100
[12301.899073]  kernfs_remove_by_name_ns+0x3b/0x80
[12301.899080]  bus_remove_driver+0x92/0xa0
[12301.899085]  acpi_video_unregister+0x24/0x40
[12301.899127]  i915_driver_unload+0x42/0x130 [i915]
[12301.899160]  i915_pci_remove+0x19/0x30 [i915]
[12301.899169]  pci_device_remove+0x36/0xb0
[12301.899176]  device_release_driver_internal+0x185/0x240
[12301.899183]  unbind_store+0xaf/0x180
[12301.899189]  kernfs_fop_write+0x104/0x190
[12301.899195]  __vfs_write+0x31/0x180
[12301.899203]  ? rcu_read_lock_sched_held+0x6f/0x80
[12301.899209]  ? rcu_sync_lockdep_assert+0x29/0x50
[12301.899216]  ? __sb_start_write+0x13c/0x1a0
[12301.899221]  ? vfs_write+0x17f/0x1b0
[12301.899227]  vfs_write+0xb9/0x1b0
[12301.899233]  ksys_write+0x50/0xc0
[12301.899239]  do_syscall_64+0x4b/0x180
[12301.899247]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
[12301.899253] RIP: 0033:0x7f452ac7f7a4
[12301.899259] Code: 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 80 00 00 00 00 8b 05 aa f0 2c 00 48 63 ff 85 c0 75 13 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 54 f3 c3 66 90 55 53 48 89 d5 48 89 f3 48 83
[12301.899273] RSP: 002b:00007ffceafa6918 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
[12301.899282] RAX: ffffffffffffffda RBX: 000000000000000d RCX: 00007f452ac7f7a4
[12301.899288] RDX: 000000000000000d RSI: 00005612a1abf7c0 RDI: 0000000000000001
[12301.899295] RBP: 00005612a1abf7c0 R08: 000000000000000a R09: 00005612a1c46730
[12301.899301] R10: 000000000000000a R11: 0000000000000246 R12: 000000000000000d
[12301.899308] R13: 0000000000000001 R14: 00007f452af4a740 R15: 000000000000000d

Looking around I've noticed that usb and i2c already handle similar
recursion problems, where a sysfs file can unbind the same type of
sysfs somewhere else in the hierarchy. Relevant commits are:

commit 356c05d
Author: Alan Stern <stern@rowland.harvard.edu>
Date:   Mon May 14 13:30:03 2012 -0400

    sysfs: get rid of some lockdep false positives

commit e9b526f
Author: Alexander Sverdlin <alexander.sverdlin@nsn.com>
Date:   Fri May 17 14:56:35 2013 +0200

    i2c: suppress lockdep warning on delete_device

Implement the same trick for driver bind/unbind.

v2: Put the macro into bus.c (Greg).

Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Ramalingam C <ramalingam.c@intel.com>
Cc: Arend van Spriel <aspriel@gmail.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Bartosz Golaszewski <brgl@bgdev.pl>
Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Cc: Vivek Gautam <vivek.gautam@codeaurora.org>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
repojohnray pushed a commit to repojohnray/linux-sunxi-4.7.y that referenced this issue Jan 26, 2019
[ Upstream commit 4f4b374 ]

This is the much more correct fix for my earlier attempt at:

https://lkml.org/lkml/2018/12/10/118

Short recap:

- There's not actually a locking issue, it's just lockdep being a bit
  too eager to complain about a possible deadlock.

- Contrary to what I claimed the real problem is recursion on
  kn->count. Greg pointed me at sysfs_break_active_protection(), used
  by the scsi subsystem to allow a sysfs file to unbind itself. That
  would be a real deadlock, which isn't what's happening here. Also,
  breaking the active protection means we'd need to manually handle
  all the lifetime fun.

- With Rafael we discussed the task_work approach, which kinda works,
  but has two downsides: It's a functional change for a lockdep
  annotation issue, and it won't work for the bind file (which needs
  to get the errno from the driver load function back to userspace).

- Greg also asked why this never showed up: To hit this you need to
  unregister a 2nd driver from the unload code of your first driver. I
  guess only gpus do that. The bug has always been there, but only
  with a recent patch series did we add more locks so that lockdep
  built a chain from unbinding the snd-hda driver to the
  acpi_video_unregister call.

Full lockdep splat:

[12301.898799] ============================================
[12301.898805] WARNING: possible recursive locking detected
[12301.898811] 4.20.0-rc7+ linux-sunxi#84 Not tainted
[12301.898815] --------------------------------------------
[12301.898821] bash/5297 is trying to acquire lock:
[12301.898826] 00000000f61c6093 (kn->count#39){++++}, at: kernfs_remove_by_name_ns+0x3b/0x80
[12301.898841] but task is already holding lock:
[12301.898847] 000000005f634021 (kn->count#39){++++}, at: kernfs_fop_write+0xdc/0x190
[12301.898856] other info that might help us debug this:
[12301.898862]  Possible unsafe locking scenario:
[12301.898867]        CPU0
[12301.898870]        ----
[12301.898874]   lock(kn->count#39);
[12301.898879]   lock(kn->count#39);
[12301.898883] *** DEADLOCK ***
[12301.898891]  May be due to missing lock nesting notation
[12301.898899] 5 locks held by bash/5297:
[12301.898903]  #0: 00000000cd800e54 (sb_writers#4){.+.+}, at: vfs_write+0x17f/0x1b0
[12301.898915]  jwrdegoede#1: 000000000465e7c2 (&of->mutex){+.+.}, at: kernfs_fop_write+0xd3/0x190
[12301.898925]  jwrdegoede#2: 000000005f634021 (kn->count#39){++++}, at: kernfs_fop_write+0xdc/0x190
[12301.898936]  jwrdegoede#3: 00000000414ef7ac (&dev->mutex){....}, at: device_release_driver_internal+0x34/0x240
[12301.898950]  jwrdegoede#4: 000000003218fbdf (register_count_mutex){+.+.}, at: acpi_video_unregister+0xe/0x40
[12301.898960] stack backtrace:
[12301.898968] CPU: 1 PID: 5297 Comm: bash Not tainted 4.20.0-rc7+ linux-sunxi#84
[12301.898974] Hardware name: Hewlett-Packard HP EliteBook 8460p/161C, BIOS 68SCF Ver. F.01 03/11/2011
[12301.898982] Call Trace:
[12301.898989]  dump_stack+0x67/0x9b
[12301.898997]  __lock_acquire+0x6ad/0x1410
[12301.899003]  ? kernfs_remove_by_name_ns+0x3b/0x80
[12301.899010]  ? find_held_lock+0x2d/0x90
[12301.899017]  ? mutex_spin_on_owner+0xe4/0x150
[12301.899023]  ? find_held_lock+0x2d/0x90
[12301.899030]  ? lock_acquire+0x90/0x180
[12301.899036]  lock_acquire+0x90/0x180
[12301.899042]  ? kernfs_remove_by_name_ns+0x3b/0x80
[12301.899049]  __kernfs_remove+0x296/0x310
[12301.899055]  ? kernfs_remove_by_name_ns+0x3b/0x80
[12301.899060]  ? kernfs_name_hash+0xd/0x80
[12301.899066]  ? kernfs_find_ns+0x6c/0x100
[12301.899073]  kernfs_remove_by_name_ns+0x3b/0x80
[12301.899080]  bus_remove_driver+0x92/0xa0
[12301.899085]  acpi_video_unregister+0x24/0x40
[12301.899127]  i915_driver_unload+0x42/0x130 [i915]
[12301.899160]  i915_pci_remove+0x19/0x30 [i915]
[12301.899169]  pci_device_remove+0x36/0xb0
[12301.899176]  device_release_driver_internal+0x185/0x240
[12301.899183]  unbind_store+0xaf/0x180
[12301.899189]  kernfs_fop_write+0x104/0x190
[12301.899195]  __vfs_write+0x31/0x180
[12301.899203]  ? rcu_read_lock_sched_held+0x6f/0x80
[12301.899209]  ? rcu_sync_lockdep_assert+0x29/0x50
[12301.899216]  ? __sb_start_write+0x13c/0x1a0
[12301.899221]  ? vfs_write+0x17f/0x1b0
[12301.899227]  vfs_write+0xb9/0x1b0
[12301.899233]  ksys_write+0x50/0xc0
[12301.899239]  do_syscall_64+0x4b/0x180
[12301.899247]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
[12301.899253] RIP: 0033:0x7f452ac7f7a4
[12301.899259] Code: 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 80 00 00 00 00 8b 05 aa f0 2c 00 48 63 ff 85 c0 75 13 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 54 f3 c3 66 90 55 53 48 89 d5 48 89 f3 48 83
[12301.899273] RSP: 002b:00007ffceafa6918 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
[12301.899282] RAX: ffffffffffffffda RBX: 000000000000000d RCX: 00007f452ac7f7a4
[12301.899288] RDX: 000000000000000d RSI: 00005612a1abf7c0 RDI: 0000000000000001
[12301.899295] RBP: 00005612a1abf7c0 R08: 000000000000000a R09: 00005612a1c46730
[12301.899301] R10: 000000000000000a R11: 0000000000000246 R12: 000000000000000d
[12301.899308] R13: 0000000000000001 R14: 00007f452af4a740 R15: 000000000000000d

Looking around I've noticed that usb and i2c already handle similar
recursion problems, where a sysfs file can unbind the same type of
sysfs somewhere else in the hierarchy. Relevant commits are:

commit 356c05d
Author: Alan Stern <stern@rowland.harvard.edu>
Date:   Mon May 14 13:30:03 2012 -0400

    sysfs: get rid of some lockdep false positives

commit e9b526f
Author: Alexander Sverdlin <alexander.sverdlin@nsn.com>
Date:   Fri May 17 14:56:35 2013 +0200

    i2c: suppress lockdep warning on delete_device

Implement the same trick for driver bind/unbind.

v2: Put the macro into bus.c (Greg).

Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Ramalingam C <ramalingam.c@intel.com>
Cc: Arend van Spriel <aspriel@gmail.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Bartosz Golaszewski <brgl@bgdev.pl>
Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Cc: Vivek Gautam <vivek.gautam@codeaurora.org>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
repojohnray pushed a commit to repojohnray/linux-sunxi-4.7.y that referenced this issue Feb 25, 2019
In process_slab(), "p = get_freepointer()" could return a tagged
pointer, but "addr = page_address()" always return a native pointer.  As
the result, slab_index() is messed up here,

    return (p - addr) / s->size;

All other callers of slab_index() have the same situation where "addr"
is from page_address(), so just need to untag "p".

    # cat /sys/kernel/slab/hugetlbfs_inode_cache/alloc_calls

    Unable to handle kernel paging request at virtual address 2bff808aa4856d48
    Mem abort info:
      ESR = 0x96000007
      Exception class = DABT (current EL), IL = 32 bits
      SET = 0, FnV = 0
      EA = 0, S1PTW = 0
    Data abort info:
      ISV = 0, ISS = 0x00000007
      CM = 0, WnR = 0
    swapper pgtable: 64k pages, 48-bit VAs, pgdp = 0000000002498338
    [2bff808aa4856d48] pgd=00000097fcfd0003, pud=00000097fcfd0003, pmd=00000097fca30003, pte=00e8008b24850712
    Internal error: Oops: 96000007 [jwrdegoede#1] SMP
    CPU: 3 PID: 79210 Comm: read_all Tainted: G             L    5.0.0-rc7+ linux-sunxi#84
    Hardware name: HPE Apollo 70             /C01_APACHE_MB         , BIOS L50_5.13_1.0.6 07/10/2018
    pstate: 00400089 (nzcv daIf +PAN -UAO)
    pc : get_map+0x78/0xec
    lr : get_map+0xa0/0xec
    sp : aeff808989e3f8e0
    x29: aeff808989e3f940 x28: ffff800826200000
    x27: ffff100012d47000 x26: 9700000000002500
    x25: 0000000000000001 x24: 52ff8008200131f8
    x23: 52ff8008200130a0 x22: 52ff800820013098
    x21: ffff800826200000 x20: ffff100013172ba0
    x19: 2bff808a8971bc00 x18: ffff1000148f5538
    x17: 000000000000001b x16: 00000000000000ff
    x15: ffff1000148f5000 x14: 00000000000000d2
    x13: 0000000000000001 x12: 0000000000000000
    x11: 0000000020000002 x10: 2bff808aa4856d48
    x9 : 0000020000000000 x8 : 68ff80082620ebb0
    x7 : 0000000000000000 x6 : ffff1000105da1dc
    x5 : 0000000000000000 x4 : 0000000000000000
    x3 : 0000000000000010 x2 : 2bff808a8971bc00
    x1 : ffff7fe002098800 x0 : ffff80082620ceb0
    Process read_all (pid: 79210, stack limit = 0x00000000f65b9361)
    Call trace:
     get_map+0x78/0xec
     process_slab+0x7c/0x47c
     list_locations+0xb0/0x3c8
     alloc_calls_show+0x34/0x40
     slab_attr_show+0x34/0x48
     sysfs_kf_seq_show+0x2e4/0x570
     kernfs_seq_show+0x12c/0x1a0
     seq_read+0x48c/0xf84
     kernfs_fop_read+0xd4/0x448
     __vfs_read+0x94/0x5d4
     vfs_read+0xcc/0x194
     ksys_read+0x6c/0xe8
     __arm64_sys_read+0x68/0xb0
     el0_svc_handler+0x230/0x3bc
     el0_svc+0x8/0xc
    Code: d3467d2a 9ac92329 8b0a0e6a f9800151 (c85f7d4b)
    ---[ end trace a383a9a44ff13176 ]---
    Kernel panic - not syncing: Fatal exception
    SMP: stopping secondary CPUs
    SMP: failed to stop secondary CPUs 1-7,32,40,127
    Kernel Offset: disabled
    CPU features: 0x002,20000c18
    Memory Limit: none
    ---[ end Kernel panic - not syncing: Fatal exception ]---

Link: http://lkml.kernel.org/r/20190220020251.82039-1-cai@lca.pw
Signed-off-by: Qian Cai <cai@lca.pw>
Reviewed-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
repojohnray pushed a commit to repojohnray/linux-sunxi-4.7.y that referenced this issue May 25, 2022
[ Upstream commit 810c2f0 ]

IPv6 addresses which are used for tunnels are stored in a hash table
with reference counting. When a new GRE tunnel is configured, the driver
is notified and configures it in hardware.

Currently, any change in the tunnel is not applied in the driver. It
means that if the remote address is changed, the driver is not aware of
this change and the first address will be used.

This behavior results in a warning [1] in scenarios such as the
following:

 # ip link add name gre1 type ip6gre local 2000::3 remote 2000::fffe tos inherit ttl inherit
 # ip link set name gre1 type ip6gre local 2000::3 remote 2000::ffff ttl inherit
 # ip link delete gre1

The change of the address is not applied in the driver. Currently, the
driver uses the remote address which is stored in the 'parms' of the
overlay device. When the tunnel is removed, the new IPv6 address is
used, the driver tries to release it, but as it is not aware of the
change, this address is not configured and it warns about releasing non
existing IPv6 address.

Fix it by using the IPv6 address which is cached in the IPIP entry, this
address is the last one that the driver used, so even in cases such the
above, the first address will be released, without any warning.

[1]:

WARNING: CPU: 1 PID: 2197 at drivers/net/ethernet/mellanox/mlxsw/spectrum.c:2920 mlxsw_sp_ipv6_addr_put+0x146/0x220 [mlxsw_spectrum]
...
CPU: 1 PID: 2197 Comm: ip Not tainted 5.17.0-rc8-custom-95062-gc1e5ded51a9a linux-sunxi#84
Hardware name: Mellanox Technologies Ltd. MSN4700/VMOD0010, BIOS 5.11 07/12/2021
RIP: 0010:mlxsw_sp_ipv6_addr_put+0x146/0x220 [mlxsw_spectrum]
...
Call Trace:
 <TASK>
 mlxsw_sp2_ipip_rem_addr_unset_gre6+0xf1/0x120 [mlxsw_spectrum]
 mlxsw_sp_netdevice_ipip_ol_event+0xdb/0x640 [mlxsw_spectrum]
 mlxsw_sp_netdevice_event+0xc4/0x850 [mlxsw_spectrum]
 raw_notifier_call_chain+0x3c/0x50
 call_netdevice_notifiers_info+0x2f/0x80
 unregister_netdevice_many+0x311/0x6d0
 rtnl_dellink+0x136/0x360
 rtnetlink_rcv_msg+0x12f/0x380
 netlink_rcv_skb+0x49/0xf0
 netlink_unicast+0x233/0x340
 netlink_sendmsg+0x202/0x440
 ____sys_sendmsg+0x1f3/0x220
 ___sys_sendmsg+0x70/0xb0
 __sys_sendmsg+0x54/0xa0
 do_syscall_64+0x35/0x80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Fixes: e846efe ("mlxsw: spectrum: Add hash table for IPv6 address mapping")
Reported-by: Maksym Yaremchuk <maksymy@nvidia.com>
Signed-off-by: Amit Cohen <amcohen@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Link: https://lore.kernel.org/r/20220511115747.238602-1-idosch@nvidia.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
repojohnray pushed a commit to repojohnray/linux-sunxi-4.7.y that referenced this issue May 28, 2022
IPv6 addresses which are used for tunnels are stored in a hash table
with reference counting. When a new GRE tunnel is configured, the driver
is notified and configures it in hardware.

Currently, any change in the tunnel is not applied in the driver. It
means that if the remote address is changed, the driver is not aware of
this change and the first address will be used.

This behavior results in a warning [1] in scenarios such as the
following:

 # ip link add name gre1 type ip6gre local 2000::3 remote 2000::fffe tos inherit ttl inherit
 # ip link set name gre1 type ip6gre local 2000::3 remote 2000::ffff ttl inherit
 # ip link delete gre1

The change of the address is not applied in the driver. Currently, the
driver uses the remote address which is stored in the 'parms' of the
overlay device. When the tunnel is removed, the new IPv6 address is
used, the driver tries to release it, but as it is not aware of the
change, this address is not configured and it warns about releasing non
existing IPv6 address.

Fix it by using the IPv6 address which is cached in the IPIP entry, this
address is the last one that the driver used, so even in cases such the
above, the first address will be released, without any warning.

[1]:

WARNING: CPU: 1 PID: 2197 at drivers/net/ethernet/mellanox/mlxsw/spectrum.c:2920 mlxsw_sp_ipv6_addr_put+0x146/0x220 [mlxsw_spectrum]
...
CPU: 1 PID: 2197 Comm: ip Not tainted 5.17.0-rc8-custom-95062-gc1e5ded51a9a linux-sunxi#84
Hardware name: Mellanox Technologies Ltd. MSN4700/VMOD0010, BIOS 5.11 07/12/2021
RIP: 0010:mlxsw_sp_ipv6_addr_put+0x146/0x220 [mlxsw_spectrum]
...
Call Trace:
 <TASK>
 mlxsw_sp2_ipip_rem_addr_unset_gre6+0xf1/0x120 [mlxsw_spectrum]
 mlxsw_sp_netdevice_ipip_ol_event+0xdb/0x640 [mlxsw_spectrum]
 mlxsw_sp_netdevice_event+0xc4/0x850 [mlxsw_spectrum]
 raw_notifier_call_chain+0x3c/0x50
 call_netdevice_notifiers_info+0x2f/0x80
 unregister_netdevice_many+0x311/0x6d0
 rtnl_dellink+0x136/0x360
 rtnetlink_rcv_msg+0x12f/0x380
 netlink_rcv_skb+0x49/0xf0
 netlink_unicast+0x233/0x340
 netlink_sendmsg+0x202/0x440
 ____sys_sendmsg+0x1f3/0x220
 ___sys_sendmsg+0x70/0xb0
 __sys_sendmsg+0x54/0xa0
 do_syscall_64+0x35/0x80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Fixes: e846efe ("mlxsw: spectrum: Add hash table for IPv6 address mapping")
Reported-by: Maksym Yaremchuk <maksymy@nvidia.com>
Signed-off-by: Amit Cohen <amcohen@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Link: https://lore.kernel.org/r/20220511115747.238602-1-idosch@nvidia.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
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