locking/atomic, sched: Unexport fetch_or()

This patch functionally reverts:

  5fd7a09cfb8c ("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. "

  e23604edac2a 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>

2 files changed, 18 insertions, 21 deletions

diff --git a/include/linux/atomic.h b/include/linux/atomic.h
index 3d64c0852164..506c3531832e 100644
--- a/include/linux/atomic.h
+++ b/include/linux/atomic.h
@@ -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
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d8465eeab8b3..8b489fcac37b 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -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,