Op 08-09-2021 om 12:14 schreef Peter Zijlstra:
On Tue, Sep 07, 2021 at 03:20:44PM +0200, Maarten Lankhorst wrote:
i915 will soon gain an eviction path that trylock a whole lot of locks for eviction, getting dmesg failures like below:
BUG: MAX_LOCK_DEPTH too low! turning off the locking correctness validator. depth: 48 max: 48! 48 locks held by i915_selftest/5776: #0: ffff888101a79240 (&dev->mutex){....}-{3:3}, at: __driver_attach+0x88/0x160 #1: ffffc900009778c0 (reservation_ww_class_acquire){+.+.}-{0:0}, at: i915_vma_pin.constprop.63+0x39/0x1b0 [i915] #2: ffff88800cf74de8 (reservation_ww_class_mutex){+.+.}-{3:3}, at: i915_vma_pin.constprop.63+0x5f/0x1b0 [i915] #3: ffff88810c7f9e38 (&vm->mutex/1){+.+.}-{3:3}, at: i915_vma_pin_ww+0x1c4/0x9d0 [i915] #4: ffff88810bad5768 (reservation_ww_class_mutex){+.+.}-{3:3}, at: i915_gem_evict_something+0x110/0x860 [i915] #5: ffff88810bad60e8 (reservation_ww_class_mutex){+.+.}-{3:3}, at: i915_gem_evict_something+0x110/0x860 [i915] ... #46: ffff88811964d768 (reservation_ww_class_mutex){+.+.}-{3:3}, at: i915_gem_evict_something+0x110/0x860 [i915] #47: ffff88811964e0e8 (reservation_ww_class_mutex){+.+.}-{3:3}, at: i915_gem_evict_something+0x110/0x860 [i915] INFO: lockdep is turned off. As an intermediate solution, add an acquire context to ww_mutex_trylock, which allows us to do proper nesting annotations on the trylocks, making the above lockdep splat disappear.
Fair enough I suppose.
+/**
- ww_mutex_trylock - tries to acquire the w/w mutex with optional acquire context
- @lock: mutex to lock
- @ctx: optional w/w acquire context
- Trylocks a mutex with the optional acquire context; no deadlock detection is
- possible. Returns 1 if the mutex has been acquired successfully, 0 otherwise.
- Unlike ww_mutex_lock, no deadlock handling is performed. However, if a @ctx is
- specified, -EALREADY and -EDEADLK handling may happen in calls to ww_mutex_lock.
- A mutex acquired with this function must be released with ww_mutex_unlock.
- */
+int __sched +ww_mutex_trylock(struct ww_mutex *ww, struct ww_acquire_ctx *ctx) +{
- bool locked;
- if (!ctx)
return mutex_trylock(&ww->base);+#ifdef CONFIG_DEBUG_MUTEXES
- DEBUG_LOCKS_WARN_ON(ww->base.magic != &ww->base);
+#endif
- preempt_disable();
- locked = __mutex_trylock(&ww->base);
- if (locked) {
ww_mutex_set_context_fastpath(ww, ctx);mutex_acquire_nest(&ww->base.dep_map, 0, 1, &ctx->dep_map, _RET_IP_);- }
- preempt_enable();
- return locked;
+} +EXPORT_SYMBOL(ww_mutex_trylock);
You'll need a similar hunk in ww_rt_mutex.c
What tree has that file?