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ipc: Replace spin_unlock_wait() with lock/unlock pair

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There is no agreed-upon definition of spin_unlock_wait()'s semantics,
and it appears that all callers could do just as well with a lock/unlock
pair.  This commit therefore replaces the spin_unlock_wait() call in
exit_sem() with spin_lock() followed immediately by spin_unlock().
This should be safe from a performance perspective because exit_sem()
is rarely invoked in production.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Andrea Parri <parri.andrea@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Manfred Spraul <manfred@colorfullife.com>
This commit is contained in:
Paul E. McKenney 2017-06-29 12:59:32 -07:00
parent 8083f29349
commit e0892e086a
1 changed files with 2 additions and 1 deletions
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3
ipc/sem.c
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@ -2091,7 +2091,8 @@ void exit_sem(struct task_struct *tsk)
* possibility where we exit while freeary() didn't * possibility where we exit while freeary() didn't
* finish unlocking sem_undo_list. * finish unlocking sem_undo_list.
*/ */
spin_unlock_wait(&ulp->lock); spin_lock(&ulp->lock);
spin_unlock(&ulp->lock);
rcu_read_unlock(); rcu_read_unlock();
break; break;
} }