diff options
| author | Chris Wilson <chris@chris-wilson.co.uk> | 2017-02-14 12:40:01 +0000 |
|---|---|---|
| committer | Gustavo Padovan <gustavo.padovan@collabora.com> | 2017-07-14 16:09:55 -0300 |
| commit | 76250f2b743b72cb685cc51ac0cdabb32957180b (patch) | |
| tree | 1775015ba5bafa7f6e09e95cff19779101954819 /drivers/dma-buf/dma-fence.c | |
| parent | e94ac3510b6a0f696f2c442c4fc4051c8101ef12 (diff) | |
dma-buf/fence: Avoid use of uninitialised timestamp
[ 236.821534] WARNING: kmemcheck: Caught 64-bit read from uninitialized memory (ffff8802538683d0)
[ 236.828642] 420000001e7f0000000000000000000000080000000000000000000000000000
[ 236.839543] i i i i u u u u i i i i i i i i u u u u u u u u u u u u u u u u
[ 236.850420] ^
[ 236.854123] RIP: 0010:[<ffffffff81396f07>] [<ffffffff81396f07>] fence_signal+0x17/0xd0
[ 236.861313] RSP: 0018:ffff88024acd7ba0 EFLAGS: 00010282
[ 236.865027] RAX: ffffffff812f6a90 RBX: ffff8802527ca800 RCX: ffff880252cb30e0
[ 236.868801] RDX: ffff88024ac5d918 RSI: ffff880252f780e0 RDI: ffff880253868380
[ 236.872579] RBP: ffff88024acd7bc0 R08: ffff88024acd7be0 R09: 0000000000000000
[ 236.876407] R10: 0000000000000000 R11: 0000000000000000 R12: ffff880253868380
[ 236.880185] R13: ffff8802538684d0 R14: ffff880253868380 R15: ffff88024cd48e00
[ 236.883983] FS: 00007f1646d1a740(0000) GS:ffff88025d000000(0000) knlGS:0000000000000000
[ 236.890959] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 236.894702] CR2: ffff880251360318 CR3: 000000024ad21000 CR4: 00000000001406f0
[ 236.898481] [<ffffffff8130d1ad>] i915_gem_request_retire+0x1cd/0x230
[ 236.902439] [<ffffffff8130e2b3>] i915_gem_request_alloc+0xa3/0x2f0
[ 236.906435] [<ffffffff812fb1bd>] i915_gem_do_execbuffer.isra.41+0xb6d/0x18b0
[ 236.910434] [<ffffffff812fc265>] i915_gem_execbuffer2+0x95/0x1e0
[ 236.914390] [<ffffffff812ad625>] drm_ioctl+0x1e5/0x460
[ 236.918275] [<ffffffff8110d4cf>] do_vfs_ioctl+0x8f/0x5c0
[ 236.922168] [<ffffffff8110da3c>] SyS_ioctl+0x3c/0x70
[ 236.926090] [<ffffffff814b7a5f>] entry_SYSCALL_64_fastpath+0x17/0x93
[ 236.930045] [<ffffffffffffffff>] 0xffffffffffffffff
We only set the timestamp before we mark the fence as signaled. It is
done before to avoid observers having a window in which they may see the
fence as complete but no timestamp. Having it does incur a potential for
the timestamp to be written twice, and even for it to be corrupted if
the u64 write is not atomic. Instead use a new bit to record the
presence of the timestamp, and teach the readers to wait until it is set
if the fence is complete. There still remains a race where the timestamp
for the signaled fence may be shown before the fence is reported as
signaled, but that's a pre-existing error.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Gustavo Padovan <gustavo@padovan.org>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Reported-by: Rafael Antognolli <rafael.antognolli@intel.com>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170214124001.1930-1-chris@chris-wilson.co.uk
Diffstat (limited to 'drivers/dma-buf/dma-fence.c')
| -rw-r--r-- | drivers/dma-buf/dma-fence.c | 17 |
1 files changed, 6 insertions, 11 deletions
diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c index 0918d3f003d6..13556fdda2a5 100644 --- a/drivers/dma-buf/dma-fence.c +++ b/drivers/dma-buf/dma-fence.c @@ -75,11 +75,6 @@ int dma_fence_signal_locked(struct dma_fence *fence) if (WARN_ON(!fence)) return -EINVAL; - if (!ktime_to_ns(fence->timestamp)) { - fence->timestamp = ktime_get(); - smp_mb__before_atomic(); - } - if (test_and_set_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) { ret = -EINVAL; @@ -87,8 +82,11 @@ int dma_fence_signal_locked(struct dma_fence *fence) * we might have raced with the unlocked dma_fence_signal, * still run through all callbacks */ - } else + } else { + fence->timestamp = ktime_get(); + set_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT, &fence->flags); trace_dma_fence_signaled(fence); + } list_for_each_entry_safe(cur, tmp, &fence->cb_list, node) { list_del_init(&cur->node); @@ -115,14 +113,11 @@ int dma_fence_signal(struct dma_fence *fence) if (!fence) return -EINVAL; - if (!ktime_to_ns(fence->timestamp)) { - fence->timestamp = ktime_get(); - smp_mb__before_atomic(); - } - if (test_and_set_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) return -EINVAL; + fence->timestamp = ktime_get(); + set_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT, &fence->flags); trace_dma_fence_signaled(fence); if (test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, &fence->flags)) { |