diff options
| author | Maarten Lankhorst <maarten.lankhorst@linux.intel.com> | 2021-09-09 11:32:18 +0200 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2021-09-17 15:08:41 +0200 |
| commit | 12235da8c80a1f9909008e4ca6036d5772b81192 (patch) | |
| tree | b6e9a7bbdc458e0909980e7b2194f9e80d092c05 /kernel/locking/ww_rt_mutex.c | |
| parent | 6880fa6c56601bb8ed59df6c30fd390cc5f6dd8f (diff) | |
kernel/locking: Add context to ww_mutex_trylock()
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.
Fixing eviction to nest into ww_class_acquire is a high priority, but
it requires a rework of the entire driver, which can only be done one
step at a time.
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.
This is also useful in regulator_lock_nested, which may avoid dropping
regulator_nesting_mutex in the uncontended path, so use it there.
TTM may be another user for this, where we could lock a buffer in a
fastpath with list locks held, without dropping all locks we hold.
[peterz: rework actual ww_mutex_trylock() implementations]
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/YUBGPdDDjKlxAuXJ@hirez.programming.kicks-ass.net
Diffstat (limited to 'kernel/locking/ww_rt_mutex.c')
| -rw-r--r-- | kernel/locking/ww_rt_mutex.c | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/kernel/locking/ww_rt_mutex.c b/kernel/locking/ww_rt_mutex.c index 3f1fff7d2780..0e00205cf467 100644 --- a/kernel/locking/ww_rt_mutex.c +++ b/kernel/locking/ww_rt_mutex.c @@ -9,6 +9,31 @@ #define WW_RT #include "rtmutex.c" +int ww_mutex_trylock(struct ww_mutex *lock, struct ww_acquire_ctx *ww_ctx) +{ + struct rt_mutex *rtm = &lock->base; + + if (!ww_ctx) + return rt_mutex_trylock(rtm); + + /* + * Reset the wounded flag after a kill. No other process can + * race and wound us here, since they can't have a valid owner + * pointer if we don't have any locks held. + */ + if (ww_ctx->acquired == 0) + ww_ctx->wounded = 0; + + if (__rt_mutex_trylock(&rtm->rtmutex)) { + ww_mutex_set_context_fastpath(lock, ww_ctx); + mutex_acquire_nest(&rtm->dep_map, 0, 1, ww_ctx->dep_map, _RET_IP_); + return 1; + } + + return 0; +} +EXPORT_SYMBOL(ww_mutex_trylock); + static int __sched __ww_rt_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ww_ctx, unsigned int state, unsigned long ip) |