From f87f3a328dbbb3e79dd53e7e889ced9222512649 Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Tue, 28 Nov 2017 18:42:18 +0000 Subject: locking/core: Fix deadlock during boot on systems with GENERIC_LOCKBREAK Commit: a8a217c22116 ("locking/core: Remove {read,spin,write}_can_lock()") removed the definition of raw_spin_can_lock(), causing the GENERIC_LOCKBREAK spin_lock() routines to poll the ->break_lock field when waiting on a lock. This has been reported to cause a deadlock during boot on s390, because the ->break_lock field is also set by the waiters, and can potentially remain set indefinitely if no other CPUs come in to take the lock after it has been released. This patch removes the explicit spinning on ->break_lock from the waiters, instead relying on the outer trylock() operation to determine when the lock is available. Reported-by: Sebastian Ott Tested-by: Sebastian Ott Signed-off-by: Will Deacon Acked-by: Peter Zijlstra Cc: Heiko Carstens Cc: Linus Torvalds Cc: Martin Schwidefsky Cc: Thomas Gleixner Fixes: a8a217c22116 ("locking/core: Remove {read,spin,write}_can_lock()") Link: http://lkml.kernel.org/r/1511894539-7988-2-git-send-email-will.deacon@arm.com Signed-off-by: Ingo Molnar --- kernel/locking/spinlock.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'kernel/locking/spinlock.c') diff --git a/kernel/locking/spinlock.c b/kernel/locking/spinlock.c index 1fd1a7543cdd..0ebb253e2199 100644 --- a/kernel/locking/spinlock.c +++ b/kernel/locking/spinlock.c @@ -68,8 +68,8 @@ void __lockfunc __raw_##op##_lock(locktype##_t *lock) \ \ if (!(lock)->break_lock) \ (lock)->break_lock = 1; \ - while ((lock)->break_lock) \ - arch_##op##_relax(&lock->raw_lock); \ + \ + arch_##op##_relax(&lock->raw_lock); \ } \ (lock)->break_lock = 0; \ } \ @@ -88,8 +88,8 @@ unsigned long __lockfunc __raw_##op##_lock_irqsave(locktype##_t *lock) \ \ if (!(lock)->break_lock) \ (lock)->break_lock = 1; \ - while ((lock)->break_lock) \ - arch_##op##_relax(&lock->raw_lock); \ + \ + arch_##op##_relax(&lock->raw_lock); \ } \ (lock)->break_lock = 0; \ return flags; \ -- cgit v1.2.3