From: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> Subject: lib/test_lockup.c: minimum fix to get it compiled on PREEMPT_RT On PREEMPT_RT the locks are quite different so they can't be tested as it is done below. The alternative is to test for the waitlock within rtmutex. This is the bare minimun to get it compiled. Problems which exist on PREEMP_RT: - none of the locks (spinlock_t, rwlock_t, mutex_t, rw_semaphore) may be acquired with disabled preemption or interrupts. If I read the code correct the it is possible to acquire a mutex_t with disabled interrupts. I don't know how to obtain a lock pointer. Technically they are not exported to userland. - memory can not be allocated with disabled preemption or interrupts even with GFP_ATOMIC. Link: https://lkml.kernel.org/r/20201028181041.xyeothhkouc3p4md@xxxxxxxxxxxxx Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> Cc: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- lib/test_lockup.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) --- a/lib/test_lockup.c~lib-test_lockup-minimum-fix-to-get-it-compiled-on-preempt_rt +++ a/lib/test_lockup.c @@ -480,6 +480,21 @@ static int __init test_lockup_init(void) return -EINVAL; #ifdef CONFIG_DEBUG_SPINLOCK +#ifdef CONFIG_PREEMPT_RT + if (test_magic(lock_spinlock_ptr, + offsetof(spinlock_t, lock.wait_lock.magic), + SPINLOCK_MAGIC) || + test_magic(lock_rwlock_ptr, + offsetof(rwlock_t, rtmutex.wait_lock.magic), + SPINLOCK_MAGIC) || + test_magic(lock_mutex_ptr, + offsetof(struct mutex, lock.wait_lock.magic), + SPINLOCK_MAGIC) || + test_magic(lock_rwsem_ptr, + offsetof(struct rw_semaphore, rtmutex.wait_lock.magic), + SPINLOCK_MAGIC)) + return -EINVAL; +#else if (test_magic(lock_spinlock_ptr, offsetof(spinlock_t, rlock.magic), SPINLOCK_MAGIC) || @@ -494,6 +509,7 @@ static int __init test_lockup_init(void) SPINLOCK_MAGIC)) return -EINVAL; #endif +#endif if ((wait_state != TASK_RUNNING || (call_cond_resched && !reacquire_locks) || _
