UbiquitousOS
/
OpenCloudOS-Kernel
mirror of https://gitee.com/OpenCloudOS/OpenCloudOS-Kernel.git
11
0
Fork 0
Code Issues Projects Releases Wiki Activity

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 <mingo@kernel.org>
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Chris Mason <clm@fb.com>
Cc: Darren Hart <dvhart@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: dave@stgolabs.net
Link: http://lkml.kernel.org/r/1455045314-8305-2-git-send-email-dave@stgolabs.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Davidlohr Bueso 2016-02-09 11:15:13 -08:00 committed by Ingo Molnar
parent e2d6f8a5f5
commit 8ad7b378d0
1 changed files with 17 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
kernel/futex.c
View File

@ -124,7 +124,7 @@
* futex_wait(futex, val); * futex_wait(futex, val);
* *
* waiters++; (a) * waiters++; (a)
* mb(); (A) <-- paired with -. * smp_mb(); (A) <-- paired with -.
* | * |
* lock(hash_bucket(futex)); | * lock(hash_bucket(futex)); |
* | * |
@ -133,7 +133,7 @@
* | sys_futex(WAKE, futex); * | sys_futex(WAKE, futex);
* | futex_wake(futex); * | futex_wake(futex);
* | * |
* `-------> mb(); (B) * `--------> smp_mb(); (B)
* if (uval == val) * if (uval == val)
* queue(); * queue();
* unlock(hash_bucket(futex)); * 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 * Ensure futex_get_mm() implies a full barrier such that
* get_futex_key() implies a full barrier. This is relied upon * 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(); 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)) { switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) {
case FUT_OFF_INODE: case FUT_OFF_INODE:
ihold(key->shared.inode); /* implies MB (B) */ ihold(key->shared.inode); /* implies smp_mb(); (B) */
break; break;
case FUT_OFF_MMSHARED: case FUT_OFF_MMSHARED:
futex_get_mm(key); /* implies MB (B) */ futex_get_mm(key); /* implies smp_mb(); (B) */
break; break;
default: 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 * mm, therefore the only purpose of calling get_futex_key_refs
* is because we need the barrier for the lockless waiter check. * 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) { if (!fshared) {
key->private.mm = mm; key->private.mm = mm;
key->private.address = address; key->private.address = address;
get_futex_key_refs(key); /* implies MB (B) */ get_futex_key_refs(key); /* implies smp_mb(); (B) */
return 0; return 0;
} }
@ -572,7 +572,7 @@ again:
key->shared.pgoff = basepage_index(page); key->shared.pgoff = basepage_index(page);
} }
get_futex_key_refs(key); /* implies MB (B) */ get_futex_key_refs(key); /* implies smp_mb(); (B) */
out: out:
unlock_page(page); unlock_page(page);
@ -1864,7 +1864,7 @@ static inline struct futex_hash_bucket *queue_lock(struct futex_q *q)
q->lock_ptr = &hb->lock; q->lock_ptr = &hb->lock;
spin_lock(&hb->lock); /* implies MB (A) */ spin_lock(&hb->lock); /* implies smp_mb(); (A) */
return hb; return hb;
} }