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

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>

1 files changed, 4 insertions, 5 deletions

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index c0331891dec1..ab3c0dc8c7ed 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -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);