linux/kernel/locking
Guenter Roeck e4a02ed2aa locking/ww_mutex: Fix runtime warning in the WW mutex selftest
If CONFIG_WW_MUTEX_SELFTEST=y is enabled, booting an image
in an arm64 virtual machine results in the following
traceback if 8 CPUs are enabled:

  DEBUG_LOCKS_WARN_ON(__owner_task(owner) != current)
  WARNING: CPU: 2 PID: 537 at kernel/locking/mutex.c:1033 __mutex_unlock_slowpath+0x1a8/0x2e0
  ...
  Call trace:
   __mutex_unlock_slowpath()
   ww_mutex_unlock()
   test_cycle_work()
   process_one_work()
   worker_thread()
   kthread()
   ret_from_fork()

If requesting b_mutex fails with -EDEADLK, the error variable
is reassigned to the return value from calling ww_mutex_lock
on a_mutex again. If this call fails, a_mutex is not locked.
It is, however, unconditionally unlocked subsequently, causing
the reported warning. Fix the problem by using two error variables.

With this change, the selftest still fails as follows:

  cyclic deadlock not resolved, ret[7/8] = -35

However, the traceback is gone.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Fixes: d1b42b800e ("locking/ww_mutex: Add kselftests for resolving ww_mutex cyclic deadlocks")
Link: http://lkml.kernel.org/r/1538516929-9734-1-git-send-email-linux@roeck-us.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2018-10-03 08:56:31 +02:00
..
lockdep_internals.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
lockdep_proc.c proc: introduce proc_create_single{,_data} 2018-05-16 07:23:35 +02:00
lockdep_states.h locking/lockdep: Rework FS_RECLAIM annotation 2017-08-10 12:29:03 +02:00
lockdep.c locking/lockdep: Delete unnecessary #include 2018-09-10 13:48:25 +02:00
locktorture.c drm pull for 4.19-rc1 2018-08-15 17:39:07 -07:00
Makefile License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
mcs_spinlock.h locking/mcs: Use smp_cond_load_acquire() in MCS spin loop 2018-04-27 09:48:49 +02:00
mutex-debug.c locking/mutex: Rework mutex::owner 2016-10-25 11:31:50 +02:00
mutex-debug.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
mutex.c locking/mutex: Fix mutex debug call and ww_mutex documentation 2018-09-10 10:05:10 +02:00
mutex.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
osq_lock.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
percpu-rwsem.c locking/percpu-rwsem: Replace waitqueue with rcuwait 2017-01-14 11:14:35 +01:00
qrwlock.c locking/qrwlock: Prevent slowpath writers getting held up by fastpath 2017-10-25 10:57:25 +02:00
qspinlock_paravirt.h locking/qspinlock: Remove duplicate clear_pending() function from PV code 2018-04-27 12:55:22 +02:00
qspinlock_stat.h locking/qspinlock: Add stat tracking for pending vs. slowpath 2018-04-27 09:48:53 +02:00
qspinlock.c locking/qspinlock: Add stat tracking for pending vs. slowpath 2018-04-27 09:48:53 +02:00
rtmutex_common.h locking/rtmutex: Handle non enqueued waiters gracefully in remove_waiter() 2018-03-28 23:01:30 +02:00
rtmutex-debug.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
rtmutex-debug.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
rtmutex.c locking/rtmutex: Allow specifying a subclass for nested locking 2018-07-25 11:22:19 +02:00
rtmutex.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
rwsem-spinlock.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
rwsem-xadd.c locking/rwsem: Simplify the is-owner-spinnable checks 2018-05-25 08:11:47 +02:00
rwsem.c locking/rwsem: Fix up_read_non_owner() warning with DEBUG_RWSEMS 2018-06-20 11:29:23 +02:00
rwsem.h locking/rwsem: Add a new RWSEM_ANONYMOUSLY_OWNED flag 2018-05-16 11:45:15 +02:00
semaphore.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/debug.h> 2017-03-02 08:42:34 +01:00
spinlock_debug.c locking/spinlock/debug: Remove spinlock lockup detection code 2017-02-10 09:09:49 +01:00
spinlock.c locking/core: Remove break_lock field when CONFIG_GENERIC_LOCKBREAK=y 2017-12-12 11:24:01 +01:00
test-ww_mutex.c locking/ww_mutex: Fix runtime warning in the WW mutex selftest 2018-10-03 08:56:31 +02:00