Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes: > [ 206.875637] BUG: KCSAN: data-race in __i915_schedule+0x7fc/0x930 [i915] > [ 206.875654] > [ 206.875666] race at unknown origin, with read to 0xffff8881f7644480 of 8 bytes by task 703 on cpu 3: > [ 206.875901] __i915_schedule+0x7fc/0x930 [i915] > [ 206.876130] __bump_priority+0x63/0x80 [i915] > [ 206.876361] __i915_sched_node_add_dependency+0x258/0x300 [i915] > [ 206.876593] i915_sched_node_add_dependency+0x50/0xa0 [i915] > [ 206.876824] i915_request_await_dma_fence+0x1da/0x530 [i915] > [ 206.877057] i915_request_await_object+0x2fe/0x470 [i915] > [ 206.877287] i915_gem_do_execbuffer+0x45dc/0x4c20 [i915] > [ 206.877517] i915_gem_execbuffer2_ioctl+0x2c3/0x580 [i915] > [ 206.877535] drm_ioctl_kernel+0xe4/0x120 > [ 206.877549] drm_ioctl+0x297/0x4c7 > [ 206.877563] ksys_ioctl+0x89/0xb0 > [ 206.877577] __x64_sys_ioctl+0x42/0x60 > [ 206.877591] do_syscall_64+0x6e/0x2c0 > [ 206.877606] entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > v2: Be safe and include mb > > References: https://gitlab.freedesktop.org/drm/intel/issues/1318 > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx> > --- > drivers/gpu/drm/i915/gt/intel_engine.h | 15 ++++++++++++++- > drivers/gpu/drm/i915/gt/intel_lrc.c | 12 +++++++----- > 2 files changed, 21 insertions(+), 6 deletions(-) > > diff --git a/drivers/gpu/drm/i915/gt/intel_engine.h b/drivers/gpu/drm/i915/gt/intel_engine.h > index 29c8c03c5caa..3644fd2b8877 100644 > --- a/drivers/gpu/drm/i915/gt/intel_engine.h > +++ b/drivers/gpu/drm/i915/gt/intel_engine.h > @@ -107,7 +107,20 @@ execlists_num_ports(const struct intel_engine_execlists * const execlists) > static inline struct i915_request * > execlists_active(const struct intel_engine_execlists *execlists) > { > - return *READ_ONCE(execlists->active); > + struct i915_request * const *cur, * const *old, *active; > + > + cur = READ_ONCE(execlists->active); > + smp_rmb(); /* pairs with overwrite protection in process_csb() */ > + do { > + old = cur; > + > + active = READ_ONCE(*cur); > + cur = READ_ONCE(execlists->active); > + > + smp_rmb(); /* and complete the seqlock retry */ > + } while (cur != old); > + > + return active; > } > > static inline void > diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c > index 3eb7adc4e057..f4b7fdfa2d63 100644 > --- a/drivers/gpu/drm/i915/gt/intel_lrc.c > +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c > @@ -2389,6 +2389,7 @@ static void process_csb(struct intel_engine_cs *engine) > > /* Point active to the new ELSP; prevent overwriting */ > WRITE_ONCE(execlists->active, execlists->pending); > + smp_wmb(); /* notify execlists_active() */ > > /* cancel old inflight, prepare for switch */ > trace_ports(execlists, "preempted", old); > @@ -2396,11 +2397,12 @@ static void process_csb(struct intel_engine_cs *engine) > execlists_schedule_out(*old++); > > /* switch pending to inflight */ > - WRITE_ONCE(execlists->active, > - memcpy(execlists->inflight, > - execlists->pending, > - execlists_num_ports(execlists) * > - sizeof(*execlists->pending))); > + memcpy(execlists->inflight, > + execlists->pending, > + execlists_num_ports(execlists) * > + sizeof(*execlists->pending)); > + smp_wmb(); /* complete the seqlock */ > + WRITE_ONCE(execlists->active, execlists->inflight); Now the memcpy bit is nicely in order, Reviewed-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx> > > WRITE_ONCE(execlists->pending[0], NULL); > } else { > -- > 2.20.1 _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
