locking/atomic, sched: Unexport fetch_or()

This patch functionally reverts:

  5fd7a09cfb ("atomic: Export fetch_or()")

During the merge Linus observed that the generic version of fetch_or()
was messy:

  " This makes the ugly "fetch_or()" macro that the scheduler used
    internally a new generic helper, and does a bad job at it. "

  e23604edac Merge branch 'timers-nohz-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Now that we have introduced atomic_fetch_or(), fetch_or() is only used
by the scheduler in order to deal with thread_info flags which type
can vary across architectures.

Lets confine fetch_or() back to the scheduler so that we encourage
future users to use the more robust and well typed atomic_t version
instead.

While at it, fetch_or() gets robustified, pasting improvements from a
previous patch by Ingo Molnar that avoids needless expression
re-evaluations in the loop.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1458830281-4255-4-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Frederic Weisbecker 2016-03-24 15:38:01 +01:00 committed by Ingo Molnar
parent f009a7a767
commit 5529578a27
2 changed files with 18 additions and 21 deletions

View File

@ -579,27 +579,6 @@ static inline int atomic_fetch_or(atomic_t *p, int mask)
}
#endif
/**
* fetch_or - perform *ptr |= mask and return old value of *ptr
* @ptr: pointer to value
* @mask: mask to OR on the value
*
* cmpxchg based fetch_or, macro so it works for different integer types
*/
#ifndef fetch_or
#define fetch_or(ptr, mask) \
({ typeof(*(ptr)) __old, __val = *(ptr); \
for (;;) { \
__old = cmpxchg((ptr), __val, __val | (mask)); \
if (__old == __val) \
break; \
__val = __old; \
} \
__old; \
})
#endif
#ifdef CONFIG_GENERIC_ATOMIC64
#include <asm-generic/atomic64.h>
#endif

View File

@ -321,6 +321,24 @@ static inline void init_hrtick(void)
}
#endif /* CONFIG_SCHED_HRTICK */
/*
* cmpxchg based fetch_or, macro so it works for different integer types
*/
#define fetch_or(ptr, mask) \
({ \
typeof(ptr) _ptr = (ptr); \
typeof(mask) _mask = (mask); \
typeof(*_ptr) _old, _val = *_ptr; \
\
for (;;) { \
_old = cmpxchg(_ptr, _val, _val | _mask); \
if (_old == _val) \
break; \
_val = _old; \
} \
_old; \
})
#if defined(CONFIG_SMP) && defined(TIF_POLLING_NRFLAG)
/*
* Atomically set TIF_NEED_RESCHED and test for TIF_POLLING_NRFLAG,