search for: wq_max_active

Using the kernel global workqueue to signal fences can lead to unexpected deadlocks. Some other work (e.g. from a different driver) could directly or indirectly depend on this fence to be signaled. However, if the WQ_MAX_ACTIVE limit is reached by waiters, this can prevent the work signaling the fence from running. While this seems fairly unlikely, it's potentially exploitable. Fixes: 39126abc5e20 ("nouveau: offload fence uevents work to workqueue") Signed-off-by: Danilo Krummrich <dakr at redhat.com&gt...

...h <dakr at redhat.com> wrote: > > > > Using the kernel global workqueue to signal fences can lead to > > unexpected deadlocks. Some other work (e.g. from a different driver) > > could directly or indirectly depend on this fence to be signaled. > > However, if the WQ_MAX_ACTIVE limit is reached by waiters, this can > > prevent the work signaling the fence from running. > > > > While this seems fairly unlikely, it's potentially exploitable. > > LGTM > > Reviewed-by: Dave Airlie <airlied at redhat.com> > > probably should go...

...t; > drivers / kernel code that, by chance, makes use of the kernel global wq as > > > > > > > well. > > > > > > > > > > > > > > Admittedly, even if, it's gonna be extremely unlikely given that > > > > > > > WQ_MAX_ACTIVE == 512. But maybe it'd be safer to use a dedicated wq. > > > > > > > > > > > > > > Also, do we need to CC stable? > > > > > > > > > > > > I pushed this to Linus at the end of last week, since the hangs in 6.7 > &...

...tity *entity = &sched->entity; - const long timeout = msecs_to_jiffies(NOUVEAU_SCHED_JOB_TIMEOUT_MS); + struct drm_sched_init_params params; int ret; + memset(&params, 0, sizeof(struct drm_sched_init_params)); + if (!wq) { wq = alloc_workqueue("nouveau_sched_wq_%d", 0, WQ_MAX_ACTIVE, current->pid); @@ -416,10 +418,18 @@ nouveau_sched_init(struct nouveau_sched *sched, struct nouveau_drm *drm, sched->wq = wq; } - ret = drm_sched_init(drm_sched, &nouveau_sched_ops, wq, - NOUVEAU_SCHED_PRIORITY_COUNT, - credit_limit, 0, timeout, - NU...