Commit-ID: 8ad7b378d0d016309014cae0f640434bca7b5e11 Gitweb: http://git.kernel.org/tip/8ad7b378d0d016309014cae0f640434bca7b5e11 Author: Davidlohr Bueso <[email protected]> AuthorDate: Tue, 9 Feb 2016 11:15:13 -0800 Committer: Ingo Molnar <[email protected]> CommitDate: Wed, 17 Feb 2016 10:42:17 +0100
futex: Rename barrier references in ordering guarantees Ingo suggested we rename how we reference barriers A and B regarding futex ordering guarantees. This patch replaces, for both barriers, MB (A) with smp_mb(); (A), such that: - We explicitly state that the barriers are SMP, and - We standardize how we reference these across futex.c helping readers follow what barrier does what and where. Suggested-by: Ingo Molnar <[email protected]> Signed-off-by: Davidlohr Bueso <[email protected]> Reviewed-by: Thomas Gleixner <[email protected]> Cc: Chris Mason <[email protected]> Cc: Darren Hart <[email protected]> Cc: Hugh Dickins <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Mel Gorman <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Sebastian Andrzej Siewior <[email protected]> Cc: [email protected] Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> --- kernel/futex.c | 34 +++++++++++++++++----------------- 1 file changed, 17 insertions(+), 17 deletions(-) diff --git a/kernel/futex.c b/kernel/futex.c index 5d6ce64..08ac700 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -124,16 +124,16 @@ * futex_wait(futex, val); * * waiters++; (a) - * mb(); (A) <-- paired with -. - * | - * lock(hash_bucket(futex)); | - * | - * uval = *futex; | - * | *futex = newval; - * | sys_futex(WAKE, futex); - * | futex_wake(futex); - * | - * `-------> mb(); (B) + * smp_mb(); (A) <-- paired with -. + * | + * lock(hash_bucket(futex)); | + * | + * uval = *futex; | + * | *futex = newval; + * | sys_futex(WAKE, futex); + * | futex_wake(futex); + * | + * `--------> smp_mb(); (B) * if (uval == val) * queue(); * unlock(hash_bucket(futex)); @@ -334,7 +334,7 @@ static inline void futex_get_mm(union futex_key *key) /* * Ensure futex_get_mm() implies a full barrier such that * get_futex_key() implies a full barrier. This is relied upon - * as full barrier (B), see the ordering comment above. + * as smp_mb(); (B), see the ordering comment above. */ smp_mb__after_atomic(); } @@ -407,10 +407,10 @@ static void get_futex_key_refs(union futex_key *key) switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) { case FUT_OFF_INODE: - ihold(key->shared.inode); /* implies MB (B) */ + ihold(key->shared.inode); /* implies smp_mb(); (B) */ break; case FUT_OFF_MMSHARED: - futex_get_mm(key); /* implies MB (B) */ + futex_get_mm(key); /* implies smp_mb(); (B) */ break; default: /* @@ -418,7 +418,7 @@ static void get_futex_key_refs(union futex_key *key) * mm, therefore the only purpose of calling get_futex_key_refs * is because we need the barrier for the lockless waiter check. */ - smp_mb(); /* explicit MB (B) */ + smp_mb(); /* explicit smp_mb(); (B) */ } } @@ -497,7 +497,7 @@ get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key, int rw) if (!fshared) { key->private.mm = mm; key->private.address = address; - get_futex_key_refs(key); /* implies MB (B) */ + get_futex_key_refs(key); /* implies smp_mb(); (B) */ return 0; } @@ -572,7 +572,7 @@ again: key->shared.pgoff = basepage_index(page); } - get_futex_key_refs(key); /* implies MB (B) */ + get_futex_key_refs(key); /* implies smp_mb(); (B) */ out: unlock_page(page); @@ -1864,7 +1864,7 @@ static inline struct futex_hash_bucket *queue_lock(struct futex_q *q) q->lock_ptr = &hb->lock; - spin_lock(&hb->lock); /* implies MB (A) */ + spin_lock(&hb->lock); /* implies smp_mb(); (A) */ return hb; }
