On Fri, Aug 06, 2021 at 11:23:06AM -0700, John Harrison wrote:
> On 7/30/2021 12:53, Matthew Brost wrote:
> > A small race exists between intel_gt_retire_requests_timeout and
> > intel_timeline_exit which could result in the syncmap not getting
> > free'd. Rather than work to hard to seal this race, simply cleanup the
> free'd -> freed
>
Sure.
> > syncmap on fini.
> >
> > unreferenced object 0xffff88813bc53b18 (size 96):
> > comm "gem_close_race", pid 5410, jiffies 4294917818 (age 1105.600s)
> > hex dump (first 32 bytes):
> > 01 00 00 00 00 00 00 00 00 00 00 00 0a 00 00 00 ................
> > 00 00 00 00 00 00 00 00 6b 6b 6b 6b 06 00 00 00 ........kkkk....
> > backtrace:
> > [<00000000120b863a>] __sync_alloc_leaf+0x1e/0x40 [i915]
> > [<00000000042f6959>] __sync_set+0x1bb/0x240 [i915]
> > [<0000000090f0e90f>] i915_request_await_dma_fence+0x1c7/0x400 [i915]
> > [<0000000056a48219>] i915_request_await_object+0x222/0x360 [i915]
> > [<00000000aaac4ee3>] i915_gem_do_execbuffer+0x1bd0/0x2250 [i915]
> > [<000000003c9d830f>] i915_gem_execbuffer2_ioctl+0x405/0xce0 [i915]
> > [<00000000fd7a8e68>] drm_ioctl_kernel+0xb0/0xf0 [drm]
> > [<00000000e721ee87>] drm_ioctl+0x305/0x3c0 [drm]
> > [<000000008b0d8986>] __x64_sys_ioctl+0x71/0xb0
> > [<0000000076c362a4>] do_syscall_64+0x33/0x80
> > [<00000000eb7a4831>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> >
> > Signed-off-by: Matthew Brost <matthew.brost@xxxxxxxxx>
> > Fixes: 531958f6f357 ("drm/i915/gt: Track timeline activeness in enter/exit")
> > Cc: <stable@xxxxxxxxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/gt/intel_timeline.c | 9 +++++++++
> > 1 file changed, 9 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/gt/intel_timeline.c b/drivers/gpu/drm/i915/gt/intel_timeline.c
> > index c4a126c8caef..1257f4f11e66 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_timeline.c
> > +++ b/drivers/gpu/drm/i915/gt/intel_timeline.c
> > @@ -127,6 +127,15 @@ static void intel_timeline_fini(struct rcu_head *rcu)
> > i915_vma_put(timeline->hwsp_ggtt);
> > i915_active_fini(&timeline->active);
> > +
> > + /*
> > + * A small race exists between intel_gt_retire_requests_timeout and
> > + * intel_timeline_exit which could result in the syncmap not getting
> > + * free'd. Rather than work to hard to seal this race, simply cleanup
> > + * the syncmap on fini.
> What is the race? I'm going round in circles just trying to work out how
> intel_gt_retire_requests_timeout is supposed to get to intel_timeline_exit
> in the first place.
>
intel_gt_retire_requests_timeout increments tl->active_count, active_count == 2
intel_timeline_exit is called, returns on atomic_add_unless, active_count == 1
intel_gt_retire_requests_timeout decrements tl->active_count, active_count == 0
i915_syncmap_free is never called, memory leak
Matt
> Also, free'd -> freed.
>
> John.
>
>
> > + */
> > + i915_syncmap_free(&timeline->sync);
> > +
> > kfree(timeline);
> > }
>
