linux-stable.git/kernel/locking/mutex.c, branch v5.4.166

locking/mutex: Fix HANDOFF condition

2021-09-15T07:47:25+00:00

[ Upstream commit 048661a1f963e9517630f080687d48af79ed784c ]

Yanfei reported that setting HANDOFF should not depend on recomputing
@first, only on @first state. Which would then give:

  if (ww_ctx || !first)
    first = __mutex_waiter_is_first(lock, &waiter);
  if (first)
    __mutex_set_flag(lock, MUTEX_FLAG_HANDOFF);

But because 'ww_ctx || !first' is basically 'always' and the test for
first is relatively cheap, omit that first branch entirely.

Reported-by: Yanfei Xu 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Waiman Long 
Reviewed-by: Yanfei Xu 
Link: https://lore.kernel.org/r/20210630154114.896786297@infradead.org
Signed-off-by: Sasha Levin

locking/mutex: clear MUTEX_FLAGS if wait_list is empty due to signal

2021-05-26T10:05:15+00:00

[ Upstream commit 3a010c493271f04578b133de977e0e5dd2848cea ]

When a interruptible mutex locker is interrupted by a signal
without acquiring this lock and removed from the wait queue.
if the mutex isn't contended enough to have a waiter
put into the wait queue again, the setting of the WAITER
bit will force mutex locker to go into the slowpath to
acquire the lock every time, so if the wait queue is empty,
the WAITER bit need to be clear.

Fixes: 040a0a371005 ("mutex: Add support for wound/wait style locks")
Suggested-by: Peter Zijlstra 
Signed-off-by: Zqiang 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20210517034005.30828-1-qiang.zhang@windriver.com
Signed-off-by: Sasha Levin

locking/ww_mutex: Simplify use_ww_ctx & ww_ctx handling

2021-04-07T12:47:40+00:00

[ Upstream commit 5de2055d31ea88fd9ae9709ac95c372a505a60fa ]

The use_ww_ctx flag is passed to mutex_optimistic_spin(), but the
function doesn't use it. The frequent use of the (use_ww_ctx && ww_ctx)
combination is repetitive.

In fact, ww_ctx should not be used at all if !use_ww_ctx.  Simplify
ww_mutex code by dropping use_ww_ctx from mutex_optimistic_spin() an
clear ww_ctx if !use_ww_ctx. In this way, we can replace (use_ww_ctx &&
ww_ctx) by just (ww_ctx).

Signed-off-by: Waiman Long 
Signed-off-by: Ingo Molnar 
Acked-by: Davidlohr Bueso 
Link: https://lore.kernel.org/r/20210316153119.13802-2-longman@redhat.com
Signed-off-by: Sasha Levin

mutex: Fix up mutex_waiter usage

2019-08-08T07:09:25+00:00

The patch moving bits into mutex.c was a little too much; by also
moving struct mutex_waiter a few less common CONFIGs would no longer
build.

Fixes: 5f35d5a66b3e ("locking/mutex: Make __mutex_owner static to mutex.c")
Signed-off-by: Peter Zijlstra (Intel)

locking/mutex: Use mutex flags macro instead of hard code

2019-08-06T10:49:16+00:00

Use the mutex flag macro instead of hard code value inside
__mutex_owner().

Signed-off-by: Mukesh Ojha 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: mingo@redhat.com
Cc: will@kernel.org
Link: https://lkml.kernel.org/r/1564585504-3543-2-git-send-email-mojha@codeaurora.org

locking/mutex: Make __mutex_owner static to mutex.c

2019-08-06T10:49:16+00:00

__mutex_owner() should only be used by the mutex api's.
So, to put this restiction let's move the __mutex_owner()
function definition from linux/mutex.h to mutex.c file.

There exist functions that uses __mutex_owner() like
mutex_is_locked() and mutex_trylock_recursive(), So
to keep legacy thing intact move them as well and
export them.

Move mutex_waiter structure also to keep it private to the
file.

Signed-off-by: Mukesh Ojha 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: mingo@redhat.com
Cc: will@kernel.org
Link: https://lkml.kernel.org/r/1564585504-3543-1-git-send-email-mojha@codeaurora.org

locking/mutex: Test for initialized mutex

2019-07-25T13:39:27+00:00

An uninitialized/ zeroed mutex will go unnoticed because there is no
check for it. There is a magic check in the unlock's slowpath path which
might go unnoticed if the unlock happens in the fastpath.

Add a ->magic check early in the mutex_lock() and mutex_trylock() path.

Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Will Deacon 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: https://lkml.kernel.org/r/20190703092125.lsdf4gpsh2plhavb@linutronix.de
Signed-off-by: Ingo Molnar

docs: locking: convert docs to ReST and rename to *.rst

2019-07-15T11:53:27+00:00

Convert the locking documents to ReST and add them to the
kernel development book where it belongs.

Most of the stuff here is just to make Sphinx to properly
parse the text file, as they're already in good shape,
not requiring massive changes in order to be parsed.

The conversion is actually:
  - add blank lines and identation in order to identify paragraphs;
  - fix tables markups;
  - add some lists markups;
  - mark literal blocks;
  - adjust title markups.

At its new index.rst, let's add a :orphan: while this is not linked to
the main index.rst file, in order to avoid build warnings.

Signed-off-by: Mauro Carvalho Chehab 
Acked-by: Federico Vaga

treewide: Add SPDX license identifier for missed files

2019-05-21T08:50:45+00:00

Add SPDX license identifiers to all files which:

 - Have no license information of any form

 - Have EXPORT_.*_SYMBOL_GPL inside which was used in the
   initial scan/conversion to ignore the file

These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:

  GPL-2.0-only

Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

kernel/locking/mutex.c: remove caller signal_pending branch predictions

2019-01-04T21:13:48+00:00

This is already done for us internally by the signal machinery.

Link: http://lkml.kernel.org/r/20181116002713.8474-2-dave@stgolabs.net
Signed-off-by: Davidlohr Bueso 
Reviewed-by: Andrew Morton 
Cc: Peter Zijlstra 
Cc: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds