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locking/lockdep: Untangle xhlock history save/restore from task independence

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Where XHLOCK_{SOFT,HARD} are save/restore points in the xhlocks[] to
ensure the temporal IRQ events don't interact with task state, the
XHLOCK_PROC is a fundament different beast that just happens to share
the interface.

The purpose of XHLOCK_PROC is to annotate independent execution inside
one task. For example workqueues, each work should appear to run in its
own 'pristine' 'task'.

Remove XHLOCK_PROC in favour of its own interface to avoid confusion.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: boqun.feng@gmail.com
Cc: david@fromorbit.com
Cc: johannes@sipsolutions.net
Cc: kernel-team@lge.com
Cc: oleg@redhat.com
Cc: tj@kernel.org
Link: http://lkml.kernel.org/r/20170829085939.ggmb6xiohw67micb@hirez.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2017-08-29 10:59:39 +02:00 • committed by Ingo Molnar
parent 7b3d61cc73
commit f52be57080
4 changed files with 48 additions and 51 deletions
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9
kernel/workqueue.c
View file

@ -2094,8 +2094,8 @@ __acquires(&pool->lock)
lock_map_acquire(&pwq->wq->lockdep_map);
lock_map_acquire(&lockdep_map);
/*
* Strictly speaking we should do start(PROC) without holding any
* locks, that is, before these two lock_map_acquire()'s.
* Strictly speaking we should mark the invariant state without holding
* any locks, that is, before these two lock_map_acquire()'s.
*
* However, that would result in:
*
@ -2107,14 +2107,14 @@ __acquires(&pool->lock)
* Which would create W1->C->W1 dependencies, even though there is no
* actual deadlock possible. There are two solutions, using a
* read-recursive acquire on the work(queue) 'locks', but this will then
* hit the lockdep limitation on recursive locks, or simly discard
* hit the lockdep limitation on recursive locks, or simply discard
* these locks.
*
* AFAICT there is no possible deadlock scenario between the
* flush_work() and complete() primitives (except for single-threaded
* workqueues), so hiding them isn't a problem.
*/
crossrelease_hist_start(XHLOCK_PROC, true);
lockdep_invariant_state(true);
trace_workqueue_execute_start(work);
worker->current_func(work);
/*
@ -2122,7 +2122,6 @@ __acquires(&pool->lock)
* point will only record its address.
*/
trace_workqueue_execute_end(work);
crossrelease_hist_end(XHLOCK_PROC);
lock_map_release(&lockdep_map);
lock_map_release(&pwq->wq->lockdep_map);