drm/i915: Use dma_resv_iter for waiting in i915_gem_object_wait_reser…

…vation.

No memory should be allocated when calling i915_gem_object_wait,
because it may be called to idle a BO when evicting memory.

Fix this by using dma_resv_iter helpers to call
i915_gem_object_wait_fence() on each fence, which cleans up the code a lot.
Also remove dma_resv_prune, it's questionably.

This will result in the following lockdep splat.

<4> [83.538517] ======================================================
<4> [83.538520] WARNING: possible circular locking dependency detected
<4> [83.538522] 5.15.0-rc5-CI-Trybot_8062+ #1 Not tainted
<4> [83.538525] ------------------------------------------------------
<4> [83.538527] gem_render_line/5242 is trying to acquire lock:
<4> [83.538530] ffffffff8275b1e0 (fs_reclaim){+.+.}-{0:0}, at: __kmalloc_track_caller+0x56/0x270
<4> [83.538538]
but task is already holding lock:
<4> [83.538540] ffff88813471d1e0 (&vm->mutex/1){+.+.}-{3:3}, at: i915_vma_pin_ww+0x1c7/0x970 [i915]
<4> [83.538638]
which lock already depends on the new lock.
<4> [83.538642]
the existing dependency chain (in reverse order) is:
<4> [83.538645]
-> #1 (&vm->mutex/1){+.+.}-{3:3}:
<4> [83.538649]        lock_acquire+0xd3/0x310
<4> [83.538654]        i915_gem_shrinker_taints_mutex+0x2d/0x50 [i915]
<4> [83.538730]        i915_address_space_init+0xf5/0x1b0 [i915]
<4> [83.538794]        ppgtt_init+0x55/0x70 [i915]
<4> [83.538856]        gen8_ppgtt_create+0x44/0x5d0 [i915]
<4> [83.538912]        i915_ppgtt_create+0x28/0xf0 [i915]
<4> [83.538971]        intel_gt_init+0x130/0x3b0 [i915]
<4> [83.539029]        i915_gem_init+0x14b/0x220 [i915]
<4> [83.539100]        i915_driver_probe+0x97e/0xdd0 [i915]
<4> [83.539149]        i915_pci_probe+0x43/0x1d0 [i915]
<4> [83.539197]        pci_device_probe+0x9b/0x110
<4> [83.539201]        really_probe+0x1b0/0x3b0
<4> [83.539205]        __driver_probe_device+0xf6/0x170
<4> [83.539208]        driver_probe_device+0x1a/0x90
<4> [83.539210]        __driver_attach+0x93/0x160
<4> [83.539213]        bus_for_each_dev+0x72/0xc0
<4> [83.539216]        bus_add_driver+0x14b/0x1f0
<4> [83.539220]        driver_register+0x66/0xb0
<4> [83.539222]        hdmi_get_spk_alloc+0x1f/0x50 [snd_hda_codec_hdmi]
<4> [83.539227]        do_one_initcall+0x53/0x2e0
<4> [83.539230]        do_init_module+0x55/0x200
<4> [83.539234]        load_module+0x2700/0x2980
<4> [83.539237]        __do_sys_finit_module+0xaa/0x110
<4> [83.539241]        do_syscall_64+0x37/0xb0
<4> [83.539244]        entry_SYSCALL_64_after_hwframe+0x44/0xae
<4> [83.539247]
-> #0 (fs_reclaim){+.+.}-{0:0}:
<4> [83.539251]        validate_chain+0xb37/0x1e70
<4> [83.539254]        __lock_acquire+0x5a1/0xb70
<4> [83.539258]        lock_acquire+0xd3/0x310
<4> [83.539260]        fs_reclaim_acquire+0x9d/0xd0
<4> [83.539264]        __kmalloc_track_caller+0x56/0x270
<4> [83.539267]        krealloc+0x48/0xa0
<4> [83.539270]        dma_resv_get_fences+0x1c3/0x280
<4> [83.539274]        i915_gem_object_wait+0x1ff/0x410 [i915]
<4> [83.539342]        i915_gem_evict_for_node+0x16b/0x440 [i915]
<4> [83.539412]        i915_gem_gtt_reserve+0xff/0x130 [i915]
<4> [83.539482]        i915_vma_pin_ww+0x765/0x970 [i915]
<4> [83.539556]        eb_validate_vmas+0x6fe/0x8e0 [i915]
<4> [83.539626]        i915_gem_do_execbuffer+0x9a6/0x20a0 [i915]
<4> [83.539693]        i915_gem_execbuffer2_ioctl+0x11f/0x2c0 [i915]
<4> [83.539759]        drm_ioctl_kernel+0xac/0x140
<4> [83.539763]        drm_ioctl+0x201/0x3d0
<4> [83.539766]        __x64_sys_ioctl+0x6a/0xa0
<4> [83.539769]        do_syscall_64+0x37/0xb0
<4> [83.539772]        entry_SYSCALL_64_after_hwframe+0x44/0xae
<4> [83.539775]
other info that might help us debug this:
<4> [83.539778]  Possible unsafe locking scenario:
<4> [83.539781]        CPU0                    CPU1
<4> [83.539783]        ----                    ----
<4> [83.539785]   lock(&vm->mutex/1);
<4> [83.539788]                                lock(fs_reclaim);
<4> [83.539791]                                lock(&vm->mutex/1);
<4> [83.539794]   lock(fs_reclaim);
<4> [83.539796]
 *** DEADLOCK ***
<4> [83.539799] 3 locks held by gem_render_line/5242:
<4> [83.539802]  #0: ffffc90000d4bbf0 (reservation_ww_class_acquire){+.+.}-{0:0}, at: i915_gem_do_execbuffer+0x8e5/0x20a0 [i915]
<4> [83.539870]  #1: ffff88811e48bae8 (reservation_ww_class_mutex){+.+.}-{3:3}, at: eb_validate_vmas+0x81/0x8e0 [i915]
<4> [83.539936]  #2: ffff88813471d1e0 (&vm->mutex/1){+.+.}-{3:3}, at: i915_vma_pin_ww+0x1c7/0x970 [i915]
<4> [83.540011]
stack backtrace:
<4> [83.540014] CPU: 2 PID: 5242 Comm: gem_render_line Not tainted 5.15.0-rc5-CI-Trybot_8062+ #1
<4> [83.540019] Hardware name: Intel(R) Client Systems NUC11TNHi3/NUC11TNBi3, BIOS TNTGL357.0038.2020.1124.1648 11/24/2020
<4> [83.540023] Call Trace:
<4> [83.540026]  dump_stack_lvl+0x56/0x7b
<4> [83.540030]  check_noncircular+0x12e/0x150
<4> [83.540034]  ? _raw_spin_unlock_irqrestore+0x50/0x60
<4> [83.540038]  validate_chain+0xb37/0x1e70
<4> [83.540042]  __lock_acquire+0x5a1/0xb70
<4> [83.540046]  lock_acquire+0xd3/0x310
<4> [83.540049]  ? __kmalloc_track_caller+0x56/0x270
<4> [83.540052]  ? find_held_lock+0x2d/0x90
<4> [83.540055]  ? dma_resv_get_fences+0x1c3/0x280
<4> [83.540058]  fs_reclaim_acquire+0x9d/0xd0
<4> [83.540061]  ? __kmalloc_track_caller+0x56/0x270
<4> [83.540064]  __kmalloc_track_caller+0x56/0x270
<4> [83.540067]  krealloc+0x48/0xa0
<4> [83.540070]  dma_resv_get_fences+0x1c3/0x280
<4> [83.540074]  i915_gem_object_wait+0x1ff/0x410 [i915]
<4> [83.540143]  i915_gem_evict_for_node+0x16b/0x440 [i915]
<4> [83.540212]  i915_gem_gtt_reserve+0xff/0x130 [i915]
<4> [83.540281]  i915_vma_pin_ww+0x765/0x970 [i915]
<4> [83.540354]  eb_validate_vmas+0x6fe/0x8e0 [i915]
<4> [83.540420]  i915_gem_do_execbuffer+0x9a6/0x20a0 [i915]
<4> [83.540485]  ? lockdep_hardirqs_on+0xbf/0x130
<4> [83.540490]  ? __lock_acquire+0x5c0/0xb70
<4> [83.540495]  i915_gem_execbuffer2_ioctl+0x11f/0x2c0 [i915]
<4> [83.540559]  ? i915_gem_do_execbuffer+0x20a0/0x20a0 [i915]
<4> [83.540622]  drm_ioctl_kernel+0xac/0x140
<4> [83.540625]  drm_ioctl+0x201/0x3d0
<4> [83.540628]  ? i915_gem_do_execbuffer+0x20a0/0x20a0 [i915]
<4> [83.540691]  __x64_sys_ioctl+0x6a/0xa0
<4> [83.540694]  do_syscall_64+0x37/0xb0
<4> [83.540697]  entry_SYSCALL_64_after_hwframe+0x44/0xae
<4> [83.540700] RIP: 0033:0x7fc314edc50b
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>

drivers/gpu/drm/i915/gem/i915_gem_wait.c

@@ -10,7 +10,6 @@
 
 #include "gt/intel_engine.h"
 
-#include "dma_resv_utils.h"
 #include "i915_gem_ioctls.h"
 #include "i915_gem_object.h"
 
@@ -37,56 +36,17 @@ i915_gem_object_wait_reservation(struct dma_resv *resv,
 				 unsigned int flags,
 				 long timeout)
 {
-	struct dma_fence *excl;
-	bool prune_fences = false;
-
-	if (flags & I915_WAIT_ALL) {
-		struct dma_fence **shared;
-		unsigned int count, i;
-		int ret;
+	struct dma_resv_iter cursor;
+	struct dma_fence *fence;
 
-		ret = dma_resv_get_fences(resv, &excl, &count, &shared);
-		if (ret)
-			return ret;
-
-		for (i = 0; i < count; i++) {
-			timeout = i915_gem_object_wait_fence(shared[i],
-							     flags, timeout);
-			if (timeout < 0)
-				break;
+	dma_resv_iter_begin(&cursor, resv, flags & I915_WAIT_ALL);
+	dma_resv_for_each_fence_unlocked(&cursor, fence) {
 
-			dma_fence_put(shared[i]);
-		}
-
-		for (; i < count; i++)
-			dma_fence_put(shared[i]);
-		kfree(shared);
-
-		/*
-		 * If both shared fences and an exclusive fence exist,
-		 * then by construction the shared fences must be later
-		 * than the exclusive fence. If we successfully wait for
-		 * all the shared fences, we know that the exclusive fence
-		 * must all be signaled. If all the shared fences are
-		 * signaled, we can prune the array and recover the
-		 * floating references on the fences/requests.
-		 */
-		prune_fences = count && timeout >= 0;
-	} else {
-		excl = dma_resv_get_excl_unlocked(resv);
+		timeout = i915_gem_object_wait_fence(fence, flags, timeout);
+		if (timeout <= 0)
+			break;
 	}
-
-	if (excl && timeout >= 0)
-		timeout = i915_gem_object_wait_fence(excl, flags, timeout);
-
-	dma_fence_put(excl);
-
-	/*
-	 * Opportunistically prune the fences iff we know they have *all* been
-	 * signaled.
-	 */
-	if (prune_fences)
-		dma_resv_prune(resv);
+	dma_resv_iter_end(&cursor);
 
 	return timeout;
 }