diff options
| author | Nicolai Hähnle <Nicolai.Haehnle@amd.com> | 2016-12-21 21:46:40 +0300 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-01-14 13:14:55 +0300 |
| commit | 27bd57aa81d976211e1b2ddbc85bec06bddeb7e3 (patch) | |
| tree | 3fc8a0b32363552b131e48b30a69b21fd4dacdf8 | |
| parent | 977625a693283dbb35b2a3f674bc0237f7347348 (diff) | |
| download | linux-27bd57aa81d976211e1b2ddbc85bec06bddeb7e3.tar.xz | |
locking/ww_mutex/Documentation: Update the design document
Document the invariants we maintain for the wait list of ww_mutexes.
Signed-off-by: Nicolai Hähnle <Nicolai.Haehnle@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Maarten Lankhorst <dev@mblankhorst.nl>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dri-devel@lists.freedesktop.org
Link: http://lkml.kernel.org/r/1482346000-9927-13-git-send-email-nhaehnle@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
| -rw-r--r-- | Documentation/locking/ww-mutex-design.txt | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/Documentation/locking/ww-mutex-design.txt b/Documentation/locking/ww-mutex-design.txt index 8a112dc304c3..34c3a1b50b9a 100644 --- a/Documentation/locking/ww-mutex-design.txt +++ b/Documentation/locking/ww-mutex-design.txt @@ -309,11 +309,15 @@ Design: normal mutex locks, which are far more common. As such there is only a small increase in code size if wait/wound mutexes are not used. + We maintain the following invariants for the wait list: + (1) Waiters with an acquire context are sorted by stamp order; waiters + without an acquire context are interspersed in FIFO order. + (2) Among waiters with contexts, only the first one can have other locks + acquired already (ctx->acquired > 0). Note that this waiter may come + after other waiters without contexts in the list. + In general, not much contention is expected. The locks are typically used to - serialize access to resources for devices. The only way to make wakeups - smarter would be at the cost of adding a field to struct mutex_waiter. This - would add overhead to all cases where normal mutexes are used, and - ww_mutexes are generally less performance sensitive. + serialize access to resources for devices. Lockdep: Special care has been taken to warn for as many cases of api abuse |