[Intel-gfx] [PATCH] drm/i915: Avoiding reclaim tainting from runtime-pm debug

[Chris Wilson]

As intel_runtime_pm_get/_put may be called from any blockable context,
we need to avoid allowing reclaim from our mallocs, as we need to
avoid tainting any mutexes held by the callers (as they may themselves
not allow for allocations as they are taken in the shrinker).

<4> [435.339331] WARNING: possible circular locking dependency detected
<4> [435.339364] 5.1.0-rc4-CI-Trybot_4116+ #1 Tainted: G     U
<4> [435.339395] ------------------------------------------------------
<4> [435.339426] gem_caching/1334 is trying to acquire lock:
<4> [435.339456] 000000004505c39b (wakeref#3){+.+.}, at: intel_engine_pm_put+0x1b/0x40 [i915]
<4> [435.339788]
but task is already holding lock:
<4> [435.339819] 00000000ee77b4ed (fs_reclaim){+.+.}, at: fs_reclaim_acquire.part.24+0x0/0x30
<4> [435.339879]
which lock already depends on the new lock.

<4> [435.339918]
the existing dependency chain (in reverse order) is:
<4> [435.339952]
-> #1 (fs_reclaim){+.+.}:
<4> [435.339998]        fs_reclaim_acquire.part.24+0x24/0x30
<4> [435.340035]        kmem_cache_alloc_trace+0x2a/0x290
<4> [435.340311]        __print_intel_runtime_pm_wakeref+0x24/0x160 [i915]
<4> [435.340590]        untrack_intel_runtime_pm_wakeref+0x16e/0x1d0 [i915]
<4> [435.340869]        intel_runtime_pm_put_unchecked+0xd/0x30 [i915]
<4> [435.341147]        __intel_wakeref_put_once+0x22/0x40 [i915]
<4> [435.341508]        i915_request_retire+0x477/0xaf0 [i915]
<4> [435.341871]        ring_retire_requests+0x86/0x160 [i915]
<4> [435.342226]        i915_retire_requests+0x58/0xc0 [i915]
<4> [435.342576]        retire_work_handler+0x5b/0x70 [i915]
<4> [435.342615]        process_one_work+0x245/0x610
<4> [435.342646]        worker_thread+0x37/0x380
<4> [435.342679]        kthread+0x119/0x130
<4> [435.342714]        ret_from_fork+0x3a/0x50
<4> [435.342739]
-> #0 (wakeref#3){+.+.}:
<4> [435.342788]        lock_acquire+0xa6/0x1c0
<4> [435.342822]        __mutex_lock+0x8c/0x960
<4> [435.342853]        atomic_dec_and_mutex_lock+0x33/0x50
<4> [435.343151]        intel_engine_pm_put+0x1b/0x40 [i915]
<4> [435.343501]        i915_request_retire+0x477/0xaf0 [i915]
<4> [435.343851]        ring_retire_requests+0x86/0x160 [i915]
<4> [435.344202]        i915_retire_requests+0x58/0xc0 [i915]
<4> [435.344543]        i915_gem_shrink+0xd8/0x5b0 [i915]
<4> [435.344835]        i915_drop_caches_set+0x17b/0x250 [i915]
<4> [435.344877]        simple_attr_write+0xb0/0xd0
<4> [435.344911]        full_proxy_write+0x51/0x80
<4> [435.344943]        vfs_write+0xbd/0x1b0
<4> [435.344972]        ksys_write+0x55/0xe0
<4> [435.345002]        do_syscall_64+0x55/0x190
<4> [435.345040]        entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/intel_runtime_pm.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
index e6d1e592225b..3107a742d8ad 100644
--- a/drivers/gpu/drm/i915/intel_runtime_pm.c
+++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
@@ -162,7 +162,7 @@ static void cancel_intel_runtime_pm_wakeref(struct drm_i915_private *i915,
 		 rpm->debug.count, atomic_read(&rpm->wakeref_count))) {
 		char *buf;
 
-		buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+		buf = kmalloc(PAGE_SIZE, GFP_NOWAIT | __GFP_NOWARN);
 		if (!buf)
 			return;
 
@@ -198,7 +198,7 @@ __print_intel_runtime_pm_wakeref(struct drm_printer *p,
 	unsigned long i;
 	char *buf;
 
-	buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+	buf = kmalloc(PAGE_SIZE, GFP_NOWAIT | __GFP_NOWARN);
 	if (!buf)
 		return;
 
@@ -282,7 +282,9 @@ void print_intel_runtime_pm_wakeref(struct drm_i915_private *i915,
 		if (dbg.count <= alloc)
 			break;
 
-		s = krealloc(dbg.owners, dbg.count * sizeof(*s), GFP_KERNEL);
+		s = krealloc(dbg.owners,
+			     dbg.count * sizeof(*s),
+			     GFP_NOWAIT | __GFP_NOWARN);
 		if (!s)
 			goto out;
 
-- 
2.20.1