exit: Replace spin_unlock_wait() with lock/unlock pair

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 do_exit()
with spin_lock() followed immediately by spin_unlock().  This should be
safe from a performance perspective because the lock is a per-task lock,
and this is happening only at task-exit time.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Andrea Parri <parri.andrea@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/exit.c b/kernel/exit.c
index c5548fa..abfbcf6 100644 (file)
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -819,7 +819,8 @@ void __noreturn do_exit(long code)
         * Ensure that we must observe the pi_state in exit_mm() ->
         * mm_release() -> exit_pi_state_list().
         */
-       raw_spin_unlock_wait(&tsk->pi_lock);
+       raw_spin_lock_irq(&tsk->pi_lock);
+       raw_spin_unlock_irq(&tsk->pi_lock);
 
        if (unlikely(in_atomic())) {
                pr_info("note: %s[%d] exited with preempt_count %d\n",