Commit 3dd2ee48 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

bit_spinlock: don't play preemption games inside the busy loop



When we are waiting for the bit-lock to be released, and are looping
over the 'cpu_relax()' should not be doing anything else - otherwise we
miss the point of trying to do the whole 'cpu_relax()'.

Do the preemption enable/disable around the loop, rather than inside of
it.

Noticed when I was looking at the code generation for the dcache
__d_drop usage, and the code just looked very odd.
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 5dd12af0
......@@ -23,12 +23,12 @@ static inline void bit_spin_lock(int bitnum, unsigned long *addr)
preempt_disable();
#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
while (unlikely(test_and_set_bit_lock(bitnum, addr))) {
while (test_bit(bitnum, addr)) {
preempt_enable();
do {
cpu_relax();
} while (test_bit(bitnum, addr));
preempt_disable();
}
}
#endif
__acquire(bitlock);
}
......
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