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authorPeter Ziljstra <peterz@infradead.org>2018-06-15 10:07:12 +0200
committerThomas Hellstrom <thellstrom@vmware.com>2018-07-03 09:42:40 +0200
commit55f036ca7e74b85e34958af3d22121c656796413 (patch)
tree37bdbcea3384bb7d315f242b03ecc2bbff135f82 /Documentation/locking
parenteab976693153b9854bfa83d131374748f6ca4280 (diff)
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locking: WW mutex cleanup
Make the WW mutex code more readable by adding comments, splitting up functions and pointing out that we're actually using the Wait-Die algorithm. Cc: Ingo Molnar <mingo@redhat.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Gustavo Padovan <gustavo@padovan.org> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Sean Paul <seanpaul@chromium.org> Cc: David Airlie <airlied@linux.ie> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Kate Stewart <kstewart@linuxfoundation.org> Cc: Philippe Ombredanne <pombredanne@nexb.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: linux-doc@vger.kernel.org Cc: linux-media@vger.kernel.org Cc: linaro-mm-sig@lists.linaro.org Co-authored-by: Thomas Hellstrom <thellstrom@vmware.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com> Acked-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'Documentation/locking')
-rw-r--r--Documentation/locking/ww-mutex-design.txt12
1 files changed, 6 insertions, 6 deletions
diff --git a/Documentation/locking/ww-mutex-design.txt b/Documentation/locking/ww-mutex-design.txt
index 34c3a1b50b9a..2fd7f2a2af21 100644
--- a/Documentation/locking/ww-mutex-design.txt
+++ b/Documentation/locking/ww-mutex-design.txt
@@ -32,10 +32,10 @@ the oldest task) wins, and the one with the higher reservation id (i.e. the
younger task) unlocks all of the buffers that it has already locked, and then
tries again.
-In the RDBMS literature this deadlock handling approach is called wait/wound:
+In the RDBMS literature this deadlock handling approach is called wait/die:
The older tasks waits until it can acquire the contended lock. The younger tasks
needs to back off and drop all the locks it is currently holding, i.e. the
-younger task is wounded.
+younger task dies.
Concepts
--------
@@ -56,9 +56,9 @@ Furthermore there are three different class of w/w lock acquire functions:
* Normal lock acquisition with a context, using ww_mutex_lock.
-* Slowpath lock acquisition on the contending lock, used by the wounded task
- after having dropped all already acquired locks. These functions have the
- _slow postfix.
+* Slowpath lock acquisition on the contending lock, used by the task that just
+ killed its transaction after having dropped all already acquired locks.
+ These functions have the _slow postfix.
From a simple semantics point-of-view the _slow functions are not strictly
required, since simply calling the normal ww_mutex_lock functions on the
@@ -220,7 +220,7 @@ mutexes are a natural fit for such a case for two reasons:
Note that this approach differs in two important ways from the above methods:
- Since the list of objects is dynamically constructed (and might very well be
- different when retrying due to hitting the -EDEADLK wound condition) there's
+ different when retrying due to hitting the -EDEADLK die condition) there's
no need to keep any object on a persistent list when it's not locked. We can
therefore move the list_head into the object itself.
- On the other hand the dynamic object list construction also means that the -EALREADY return