[CI run] libbpf: Improve probing for memcg-based memory accounting #13
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To ensure that memory accounting will not hinder the load of BPF objects, libbpf may raise the memlock rlimit before proceeding to some operations. Whether this limit needs to be raised depends on the version of the kernel: newer versions use cgroup-based (memcg) memory accounting, and do not require any adjustment. There is a probe in libbpf to determine whether memcg-based accounting is supported. But this probe currently relies on the availability of a given BPF helper, bpf_ktime_get_coarse_ns(), which landed in the same kernel version as the memory accounting change. This works in the generic case, but it may fail, for example, if the helper function has been backported to an older kernel. This has been observed for Google Cloud's Container-Optimized OS (COS), where the helper is available but rlimit is still in use. The probe succeeds, the rlimit is not raised, and probing features with bpftool, for example, fails. Here we attempt to improve this probe and to effectively rely on memory accounting. Function probe_memcg_account() in libbpf is updated to set the rlimit to 0, then attempt to load a BPF object, and then to reset the rlimit. If the load still succeeds, then this means we're running with memcg-based accounting. This probe was inspired by the similar one from the cilium/ebpf Go library [0]. [0] https://github.com/cilium/ebpf/blob/v0.9.0/rlimit/rlimit.go#L39 Signed-off-by: Quentin Monnet <quentin@isovalent.com>
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ASAN reports an use-after-free in btf_dump_name_dups:
ERROR: AddressSanitizer: heap-use-after-free on address 0xffff927006db at pc 0xaaaab5dfb618 bp 0xffffdd89b890 sp 0xffffdd89b928
READ of size 2 at 0xffff927006db thread T0
#0 0xaaaab5dfb614 in __interceptor_strcmp.part.0 (test_progs+0x21b614)
#1 0xaaaab635f144 in str_equal_fn tools/lib/bpf/btf_dump.c:127
#2 0xaaaab635e3e0 in hashmap_find_entry tools/lib/bpf/hashmap.c:143
#3 0xaaaab635e72c in hashmap__find tools/lib/bpf/hashmap.c:212
#4 0xaaaab6362258 in btf_dump_name_dups tools/lib/bpf/btf_dump.c:1525
#5 0xaaaab636240c in btf_dump_resolve_name tools/lib/bpf/btf_dump.c:1552
#6 0xaaaab6362598 in btf_dump_type_name tools/lib/bpf/btf_dump.c:1567
#7 0xaaaab6360b48 in btf_dump_emit_struct_def tools/lib/bpf/btf_dump.c:912
#8 0xaaaab6360630 in btf_dump_emit_type tools/lib/bpf/btf_dump.c:798
#9 0xaaaab635f720 in btf_dump__dump_type tools/lib/bpf/btf_dump.c:282
#10 0xaaaab608523c in test_btf_dump_incremental tools/testing/selftests/bpf/prog_tests/btf_dump.c:236
#11 0xaaaab6097530 in test_btf_dump tools/testing/selftests/bpf/prog_tests/btf_dump.c:875
#12 0xaaaab6314ed0 in run_one_test tools/testing/selftests/bpf/test_progs.c:1062
#13 0xaaaab631a0a8 in main tools/testing/selftests/bpf/test_progs.c:1697
#14 0xffff9676d214 in __libc_start_main ../csu/libc-start.c:308
#15 0xaaaab5d65990 (test_progs+0x185990)
0xffff927006db is located 11 bytes inside of 16-byte region [0xffff927006d0,0xffff927006e0)
freed by thread T0 here:
#0 0xaaaab5e2c7c4 in realloc (test_progs+0x24c7c4)
#1 0xaaaab634f4a0 in libbpf_reallocarray tools/lib/bpf/libbpf_internal.h:191
#2 0xaaaab634f840 in libbpf_add_mem tools/lib/bpf/btf.c:163
#3 0xaaaab636643c in strset_add_str_mem tools/lib/bpf/strset.c:106
#4 0xaaaab6366560 in strset__add_str tools/lib/bpf/strset.c:157
#5 0xaaaab6352d70 in btf__add_str tools/lib/bpf/btf.c:1519
#6 0xaaaab6353e10 in btf__add_field tools/lib/bpf/btf.c:2032
#7 0xaaaab6084fcc in test_btf_dump_incremental tools/testing/selftests/bpf/prog_tests/btf_dump.c:232
#8 0xaaaab6097530 in test_btf_dump tools/testing/selftests/bpf/prog_tests/btf_dump.c:875
#9 0xaaaab6314ed0 in run_one_test tools/testing/selftests/bpf/test_progs.c:1062
#10 0xaaaab631a0a8 in main tools/testing/selftests/bpf/test_progs.c:1697
#11 0xffff9676d214 in __libc_start_main ../csu/libc-start.c:308
#12 0xaaaab5d65990 (test_progs+0x185990)
previously allocated by thread T0 here:
#0 0xaaaab5e2c7c4 in realloc (test_progs+0x24c7c4)
#1 0xaaaab634f4a0 in libbpf_reallocarray tools/lib/bpf/libbpf_internal.h:191
#2 0xaaaab634f840 in libbpf_add_mem tools/lib/bpf/btf.c:163
#3 0xaaaab636643c in strset_add_str_mem tools/lib/bpf/strset.c:106
#4 0xaaaab6366560 in strset__add_str tools/lib/bpf/strset.c:157
#5 0xaaaab6352d70 in btf__add_str tools/lib/bpf/btf.c:1519
#6 0xaaaab6353ff0 in btf_add_enum_common tools/lib/bpf/btf.c:2070
#7 0xaaaab6354080 in btf__add_enum tools/lib/bpf/btf.c:2102
#8 0xaaaab6082f50 in test_btf_dump_incremental tools/testing/selftests/bpf/prog_tests/btf_dump.c:162
#9 0xaaaab6097530 in test_btf_dump tools/testing/selftests/bpf/prog_tests/btf_dump.c:875
#10 0xaaaab6314ed0 in run_one_test tools/testing/selftests/bpf/test_progs.c:1062
#11 0xaaaab631a0a8 in main tools/testing/selftests/bpf/test_progs.c:1697
#12 0xffff9676d214 in __libc_start_main ../csu/libc-start.c:308
#13 0xaaaab5d65990 (test_progs+0x185990)
The reason is that the key stored in hash table name_map is a string
address, and the string memory is allocated by realloc() function, when
the memory is resized by realloc() later, the old memory may be freed,
so the address stored in name_map references to a freed memory, causing
use-after-free.
Fix it by storing duplicated string address in name_map.
Fixes: 919d2b1 ("libbpf: Allow modification of BTF and add btf__add_str API")
Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/bpf/20221011120108.782373-2-xukuohai@huaweicloud.com
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While setting up a new lab, I accidentally misconfigured the Ethernet port for a system that tried an NFS mount using RoCE. This made the NFS server unreachable. The following WARNING popped on the NFS client while waiting for the mount attempt to time out: kernel: workqueue: WQ_MEM_RECLAIM xprtiod:xprt_rdma_connect_worker [rpcrdma] is flushing !WQ_MEM_RECLAI> kernel: WARNING: CPU: 0 PID: 100 at kernel/workqueue.c:2628 check_flush_dependency+0xbf/0xca kernel: Modules linked in: rpcsec_gss_krb5 nfsv4 dns_resolver nfs 8021q garp stp mrp llc rfkill rpcrdma> kernel: CPU: 0 PID: 100 Comm: kworker/u8:8 Not tainted 6.0.0-rc1-00002-g6229f8c054e5 #13 kernel: Hardware name: Supermicro X10SRA-F/X10SRA-F, BIOS 2.0b 06/12/2017 kernel: Workqueue: xprtiod xprt_rdma_connect_worker [rpcrdma] kernel: RIP: 0010:check_flush_dependency+0xbf/0xca kernel: Code: 75 2a 48 8b 55 18 48 8d 8b b0 00 00 00 4d 89 e0 48 81 c6 b0 00 00 00 48 c7 c7 65 33 2e be> kernel: RSP: 0018:ffffb562806cfcf8 EFLAGS: 00010092 kernel: RAX: 0000000000000082 RBX: ffff97894f8c3c00 RCX: 0000000000000027 kernel: RDX: 0000000000000002 RSI: ffffffffbe3447d1 RDI: 00000000ffffffff kernel: RBP: ffff978941315840 R08: 0000000000000000 R09: 0000000000000000 kernel: R10: 00000000000008b0 R11: 0000000000000001 R12: ffffffffc0ce3731 kernel: R13: ffff978950c00500 R14: ffff97894341f0c0 R15: ffff978951112eb0 kernel: FS: 0000000000000000(0000) GS:ffff97987fc00000(0000) knlGS:0000000000000000 kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 kernel: CR2: 00007f807535eae8 CR3: 000000010b8e4002 CR4: 00000000003706f0 kernel: DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 kernel: DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 kernel: Call Trace: kernel: <TASK> kernel: __flush_work.isra.0+0xaf/0x188 kernel: ? _raw_spin_lock_irqsave+0x2c/0x37 kernel: ? lock_timer_base+0x38/0x5f kernel: __cancel_work_timer+0xea/0x13d kernel: ? preempt_latency_start+0x2b/0x46 kernel: rdma_addr_cancel+0x70/0x81 [ib_core] kernel: _destroy_id+0x1a/0x246 [rdma_cm] kernel: rpcrdma_xprt_connect+0x115/0x5ae [rpcrdma] kernel: ? _raw_spin_unlock+0x14/0x29 kernel: ? raw_spin_rq_unlock_irq+0x5/0x10 kernel: ? finish_task_switch.isra.0+0x171/0x249 kernel: xprt_rdma_connect_worker+0x3b/0xc7 [rpcrdma] kernel: process_one_work+0x1d8/0x2d4 kernel: worker_thread+0x18b/0x24f kernel: ? rescuer_thread+0x280/0x280 kernel: kthread+0xf4/0xfc kernel: ? kthread_complete_and_exit+0x1b/0x1b kernel: ret_from_fork+0x22/0x30 kernel: </TASK> SUNRPC's xprtiod workqueue is WQ_MEM_RECLAIM, so any workqueue that one of its work items tries to cancel has to be WQ_MEM_RECLAIM to prevent a priority inversion. The internal workqueues in the RDMA/core are currently non-MEM_RECLAIM. Jason Gunthorpe says this about the current state of RDMA/core: > If you attempt to do a reconnection/etc from within a RECLAIM > context it will deadlock on one of the many allocations that are > made to support opening the connection. > > The general idea of reclaim is that the entire task context > working under the reclaim is marked with an override of the gfp > flags to make all allocations under that call chain reclaim safe. > > But rdmacm does allocations outside this, eg in the WQs processing > the CM packets. So this doesn't work and we will deadlock. > > Fixing it is a big deal and needs more than poking WQ_MEM_RECLAIM > here and there. So we will change the ULP in this case to avoid the use of WQ_MEM_RECLAIM where possible. Deadlocks that were possible before are not fixed, but at least we no longer have a false sense of confidence that the stack won't allocate memory during memory reclaim. Suggested-by: Leon Romanovsky <leon@kernel.org> Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
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Poll CQ functions shouldn't sleep as they are called in atomic context. The following splat appears once the mlx5_aso_poll_cq() is used in such flow. BUG: scheduling while atomic: swapper/17/0/0x00000100 Modules linked in: sch_ingress openvswitch nsh mlx5_vdpa vringh vhost_iotlb vdpa mlx5_ib mlx5_core xt_conntrack xt_MASQUERADE nf_conntrack_netlink nfnetlink xt_addrtype iptable_nat nf_nat br_netfilter overlay rpcrdma rdma_ucm ib_iser libiscsi scsi_transport_iscsi ib_umad rdma_cm ib_ipoib iw_cm ib_cm ib_uverbs ib_core fuse [last unloaded: mlx5_core] CPU: 17 PID: 0 Comm: swapper/17 Tainted: G W 6.0.0-rc2+ #13 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 Call Trace: <IRQ> dump_stack_lvl+0x34/0x44 __schedule_bug.cold+0x47/0x53 __schedule+0x4b6/0x670 ? hrtimer_start_range_ns+0x28d/0x360 schedule+0x50/0x90 schedule_hrtimeout_range_clock+0x98/0x120 ? __hrtimer_init+0xb0/0xb0 usleep_range_state+0x60/0x90 mlx5_aso_poll_cq+0xad/0x190 [mlx5_core] mlx5e_ipsec_aso_update_curlft+0x81/0xb0 [mlx5_core] xfrm_timer_handler+0x6b/0x360 ? xfrm_find_acq_byseq+0x50/0x50 __hrtimer_run_queues+0x139/0x290 hrtimer_run_softirq+0x7d/0xe0 __do_softirq+0xc7/0x272 irq_exit_rcu+0x87/0xb0 sysvec_apic_timer_interrupt+0x72/0x90 </IRQ> <TASK> asm_sysvec_apic_timer_interrupt+0x16/0x20 RIP: 0010:default_idle+0x18/0x20 Code: ae 7d ff ff cc cc cc cc cc cc cc cc cc cc cc cc cc cc 0f 1f 44 00 00 8b 05 b5 30 0d 01 85 c0 7e 07 0f 00 2d 0a e3 53 00 fb f4 <c3> 0f 1f 80 00 00 00 00 0f 1f 44 00 00 65 48 8b 04 25 80 ad 01 00 RSP: 0018:ffff888100883ee0 EFLAGS: 00000242 RAX: 0000000000000001 RBX: ffff888100849580 RCX: 4000000000000000 RDX: 0000000000000001 RSI: 0000000000000083 RDI: 000000000008863c RBP: 0000000000000011 R08: 00000064e6977fa9 R09: 0000000000000001 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 default_idle_call+0x37/0xb0 do_idle+0x1cd/0x1e0 cpu_startup_entry+0x19/0x20 start_secondary+0xfe/0x120 secondary_startup_64_no_verify+0xcd/0xdb </TASK> softirq: huh, entered softirq 8 HRTIMER 00000000a97c08cb with preempt_count 00000100, exited with 00000000? Signed-off-by: Leon Romanovsky <leonro@nvidia.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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Add support precision backtracking in the presence of subprogram frames in
jump history.
This means supporting a few different kinds of subprogram invocation
situations, all requiring a slightly different handling in precision
backtracking handling logic:
- static subprogram calls;
- global subprogram calls;
- callback-calling helpers/kfuncs.
For each of those we need to handle a few precision propagation cases:
- what to do with precision of subprog returns (r0);
- what to do with precision of input arguments;
- for all of them callee-saved registers in caller function should be
propagated ignoring subprog/callback part of jump history.
N.B. Async callback-calling helpers (currently only
bpf_timer_set_callback()) are transparent to all this because they set
a separate async callback environment and thus callback's history is not
shared with main program's history. So as far as all the changes in this
commit goes, such helper is just a regular helper.
Let's look at all these situation in more details. Let's start with
static subprogram being called, using an exxerpt of a simple main
program and its static subprog, indenting subprog's frame slightly to
make everything clear.
frame 0 frame 1 precision set
======= ======= =============
9: r6 = 456;
10: r1 = 123; fr0: r6
11: call pc+10; fr0: r1, r6
22: r0 = r1; fr0: r6; fr1: r1
23: exit fr0: r6; fr1: r0
12: r1 = <map_pointer> fr0: r0, r6
13: r1 += r0; fr0: r0, r6
14: r1 += r6; fr0: r6
15: exit
As can be seen above main function is passing 123 as single argument to
an identity (`return x;`) subprog. Returned value is used to adjust map
pointer offset, which forces r0 to be marked as precise. Then
instruction #14 does the same for callee-saved r6, which will have to be
backtracked all the way to instruction #9. For brevity, precision sets
for instruction #13 and #14 are combined in the diagram above.
First, for subprog calls, r0 returned from subprog (in frame 0) has to
go into subprog's frame 1, and should be cleared from frame 0. So we go
back into subprog's frame knowing we need to mark r0 precise. We then
see that insn torvalds#22 sets r0 from r1, so now we care about marking r1
precise. When we pop up from subprog's frame back into caller at
insn #11 we keep r1, as it's an argument-passing register, so we eventually
find `10: r1 = 123;` and satify precision propagation chain for insn #13.
This example demonstrates two sets of rules:
- r0 returned after subprog call has to be moved into subprog's r0 set;
- *static* subprog arguments (r1-r5) are moved back to caller precision set.
Let's look at what happens with callee-saved precision propagation. Insn #14
mark r6 as precise. When we get into subprog's frame, we keep r6 in
frame 0's precision set *only*. Subprog itself has its own set of
independent r6-r10 registers and is not affected. When we eventually
made our way out of subprog frame we keep r6 in precision set until we
reach `9: r6 = 456;`, satisfying propagation. r6-r10 propagation is
perhaps the simplest aspect, it always stays in its original frame.
That's pretty much all we have to do to support precision propagation
across *static subprog* invocation.
Let's look at what happens when we have global subprog invocation.
frame 0 frame 1 precision set
======= ======= =============
9: r6 = 456;
10: r1 = 123; fr0: r6
11: call pc+10; # global subprog fr0: r6
12: r1 = <map_pointer> fr0: r0, r6
13: r1 += r0; fr0: r0, r6
14: r1 += r6; fr0: r6;
15: exit
Starting from insn #13, r0 has to be precise. We backtrack all the way
to insn #11 (call pc+10) and see that subprog is global, so was already
validated in isolation. As opposed to static subprog, global subprog
always returns unknown scalar r0, so that satisfies precision
propagation and we drop r0 from precision set. We are done for insns #13.
Now for insn #14. r6 is in precision set, we backtrack to `call pc+10;`.
Here we need to recognize that this is effectively both exit and entry
to global subprog, which means we stay in caller's frame. So we carry on
with r6 still in precision set, until we satisfy it at insn #9. The only
hard part with global subprogs is just knowing when it's a global func.
Lastly, callback-calling helpers and kfuncs do simulate subprog calls,
so jump history will have subprog instructions in between caller
program's instructions, but the rules of propagating r0 and r1-r5
differ, because we don't actually directly call callback. We actually
call helper/kfunc, which at runtime will call subprog, so the only
difference between normal helper/kfunc handling is that we need to make
sure to skip callback simulatinog part of jump history.
Let's look at an example to make this clearer.
frame 0 frame 1 precision set
======= ======= =============
8: r6 = 456;
9: r1 = 123; fr0: r6
10: r2 = &callback; fr0: r6
11: call bpf_loop; fr0: r6
22: r0 = r1; fr0: r6 fr1:
23: exit fr0: r6 fr1:
12: r1 = <map_pointer> fr0: r0, r6
13: r1 += r0; fr0: r0, r6
14: r1 += r6; fr0: r6;
15: exit
Again, insn #13 forces r0 to be precise. As soon as we get to `23: exit`
we see that this isn't actually a static subprog call (it's `call
bpf_loop;` helper call instead). So we clear r0 from precision set.
For callee-saved register, there is no difference: it stays in frame 0's
precision set, we go through insn torvalds#22 and torvalds#23, ignoring them until we
get back to caller frame 0, eventually satisfying precision backtrack
logic at insn #8 (`r6 = 456;`).
Assuming callback needed to set r0 as precise at insn torvalds#23, we'd
backtrack to insn torvalds#22, switching from r0 to r1, and then at the point
when we pop back to frame 0 at insn #11, we'll clear r1-r5 from
precision set, as we don't really do a subprog call directly, so there
is no input argument precision propagation.
That's pretty much it. With these changes, it seems like the only still
unsupported situation for precision backpropagation is the case when
program is accessing stack through registers other than r10. This is
still left as unsupported (though rare) case for now.
As for results. For selftests, few positive changes for bigger programs,
cls_redirect in dynptr variant benefitting the most:
[vmuser@archvm bpf]$ ./veristat -C ~/subprog-precise-before-results.csv ~/subprog-precise-after-results.csv -f @veristat.cfg -e file,prog,insns -f 'insns_diff!=0'
File Program Insns (A) Insns (B) Insns (DIFF)
---------------------------------------- ------------- --------- --------- ----------------
pyperf600_bpf_loop.bpf.linked1.o on_event 2060 2002 -58 (-2.82%)
test_cls_redirect_dynptr.bpf.linked1.o cls_redirect 15660 2914 -12746 (-81.39%)
test_cls_redirect_subprogs.bpf.linked1.o cls_redirect 61620 59088 -2532 (-4.11%)
xdp_synproxy_kern.bpf.linked1.o syncookie_tc 109980 86278 -23702 (-21.55%)
xdp_synproxy_kern.bpf.linked1.o syncookie_xdp 97716 85147 -12569 (-12.86%)
Cilium progress don't really regress. They don't use subprogs and are
mostly unaffected, but some other fixes and improvements could have
changed something. This doesn't appear to be the case:
[vmuser@archvm bpf]$ ./veristat -C ~/subprog-precise-before-results-cilium.csv ~/subprog-precise-after-results-cilium.csv -e file,prog,insns -f 'insns_diff!=0'
File Program Insns (A) Insns (B) Insns (DIFF)
------------- ------------------------------ --------- --------- ------------
bpf_host.o tail_nodeport_nat_ingress_ipv6 4983 5003 +20 (+0.40%)
bpf_lxc.o tail_nodeport_nat_ingress_ipv6 4983 5003 +20 (+0.40%)
bpf_overlay.o tail_nodeport_nat_ingress_ipv6 4983 5003 +20 (+0.40%)
bpf_xdp.o tail_handle_nat_fwd_ipv6 12475 12504 +29 (+0.23%)
bpf_xdp.o tail_nodeport_nat_ingress_ipv6 6363 6371 +8 (+0.13%)
Looking at (somewhat anonymized) Meta production programs, we see mostly
insignificant variation in number of instructions, with one program
(syar_bind6_protect6) benefitting the most at -17%.
[vmuser@archvm bpf]$ ./veristat -C ~/subprog-precise-before-results-fbcode.csv ~/subprog-precise-after-results-fbcode.csv -e prog,insns -f 'insns_diff!=0'
Program Insns (A) Insns (B) Insns (DIFF)
------------------------ --------- --------- ----------------
on_request_context_event 597 585 -12 (-2.01%)
read_async_py_stack 43789 43657 -132 (-0.30%)
read_sync_py_stack 35041 37599 +2558 (+7.30%)
rrm_usdt 946 940 -6 (-0.63%)
sysarmor_inet6_bind 28863 28249 -614 (-2.13%)
sysarmor_inet_bind 28845 28240 -605 (-2.10%)
syar_bind4_protect4 154145 147640 -6505 (-4.22%)
syar_bind6_protect6 165242 137088 -28154 (-17.04%)
syar_task_exit_setgid 21289 19720 -1569 (-7.37%)
syar_task_exit_setuid 21290 19721 -1569 (-7.37%)
do_uprobe 19967 19413 -554 (-2.77%)
tw_twfw_ingress 215877 204833 -11044 (-5.12%)
tw_twfw_tc_in 215877 204833 -11044 (-5.12%)
But checking duration (wall clock) differences, that is the actual time taken
by verifier to validate programs, we see a sometimes dramatic improvements, all
the way to about 16x improvements:
[vmuser@archvm bpf]$ ./veristat -C ~/subprog-precise-before-results-meta.csv ~/subprog-precise-after-results-meta.csv -e prog,duration -s duration_diff^ | head -n20
Program Duration (us) (A) Duration (us) (B) Duration (us) (DIFF)
---------------------------------------- ----------------- ----------------- --------------------
tw_twfw_ingress 4488374 272836 -4215538 (-93.92%)
tw_twfw_tc_in 4339111 268175 -4070936 (-93.82%)
tw_twfw_egress 3521816 270751 -3251065 (-92.31%)
tw_twfw_tc_eg 3472878 284294 -3188584 (-91.81%)
balancer_ingress 343119 291391 -51728 (-15.08%)
syar_bind6_protect6 78992 64782 -14210 (-17.99%)
ttls_tc_ingress 11739 8176 -3563 (-30.35%)
kprobe__security_inode_link 13864 11341 -2523 (-18.20%)
read_sync_py_stack 21927 19442 -2485 (-11.33%)
read_async_py_stack 30444 28136 -2308 (-7.58%)
syar_task_exit_setuid 10256 8440 -1816 (-17.71%)
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230505043317.3629845-9-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Oct 26, 2023
The following call trace shows a deadlock issue due to recursive locking of mutex "device_mutex". First lock acquire is in target_for_each_device() and second in target_free_device(). PID: 148266 TASK: ffff8be21ffb5d00 CPU: 10 COMMAND: "iscsi_ttx" #0 [ffffa2bfc9ec3b18] __schedule at ffffffffa8060e7f #1 [ffffa2bfc9ec3ba0] schedule at ffffffffa8061224 #2 [ffffa2bfc9ec3bb8] schedule_preempt_disabled at ffffffffa80615ee #3 [ffffa2bfc9ec3bc8] __mutex_lock at ffffffffa8062fd7 #4 [ffffa2bfc9ec3c40] __mutex_lock_slowpath at ffffffffa80631d3 #5 [ffffa2bfc9ec3c50] mutex_lock at ffffffffa806320c #6 [ffffa2bfc9ec3c68] target_free_device at ffffffffc0935998 [target_core_mod] #7 [ffffa2bfc9ec3c90] target_core_dev_release at ffffffffc092f975 [target_core_mod] #8 [ffffa2bfc9ec3ca0] config_item_put at ffffffffa79d250f #9 [ffffa2bfc9ec3cd0] config_item_put at ffffffffa79d2583 #10 [ffffa2bfc9ec3ce0] target_devices_idr_iter at ffffffffc0933f3a [target_core_mod] #11 [ffffa2bfc9ec3d00] idr_for_each at ffffffffa803f6fc #12 [ffffa2bfc9ec3d60] target_for_each_device at ffffffffc0935670 [target_core_mod] #13 [ffffa2bfc9ec3d98] transport_deregister_session at ffffffffc0946408 [target_core_mod] #14 [ffffa2bfc9ec3dc8] iscsit_close_session at ffffffffc09a44a6 [iscsi_target_mod] #15 [ffffa2bfc9ec3df0] iscsit_close_connection at ffffffffc09a4a88 [iscsi_target_mod] #16 [ffffa2bfc9ec3df8] finish_task_switch at ffffffffa76e5d07 #17 [ffffa2bfc9ec3e78] iscsit_take_action_for_connection_exit at ffffffffc0991c23 [iscsi_target_mod] #18 [ffffa2bfc9ec3ea0] iscsi_target_tx_thread at ffffffffc09a403b [iscsi_target_mod] #19 [ffffa2bfc9ec3f08] kthread at ffffffffa76d8080 #20 [ffffa2bfc9ec3f50] ret_from_fork at ffffffffa8200364 Fixes: 36d4cb4 ("scsi: target: Avoid that EXTENDED COPY commands trigger lock inversion") Signed-off-by: Junxiao Bi <junxiao.bi@oracle.com> Link: https://lore.kernel.org/r/20230918225848.66463-1-junxiao.bi@oracle.com Reviewed-by: Mike Christie <michael.christie@oracle.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
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