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futex: add double_unlock_hb()

Browse Source 
Impact: cleanup

The futex code uses double_lock_hb() which locks the hb->lock's
in pointer value order.  There is no parallel unlock routine,
and the code unlocks them in name order, ignoring pointer value.

This patch adds double_unlock_hb() to refactor the duplicated
code segments.

Build and boot tested on a 4 way Intel x86_64 workstation.
Passes basic pthread_mutex and PI tests out of
ltp/testcases/realtime.

Signed-off-by: Darren Hart <dvhltc@us.ibm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
LKML-Reference: <20090312075552.9856.48021.stgit@Aeon>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Darren Hart 2009-03-12 00:55:52 -07:00 committed by Ingo Molnar
parent de87fcc124
commit 5eb3dc62fc
1 changed files with 17 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
kernel/futex.c
View File

@ -690,6 +690,19 @@ double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2)
}
}
static inline void
double_unlock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2)
{
if (hb1 <= hb2) {
spin_unlock(&hb2->lock);
if (hb1 < hb2)
spin_unlock(&hb1->lock);
} else { /* hb1 > hb2 */
spin_unlock(&hb1->lock);
spin_unlock(&hb2->lock);
}
}
/*
* Wake up waiters matching bitset queued on this futex (uaddr).
*/
@ -767,9 +780,7 @@ retry:
if (unlikely(op_ret < 0)) {
u32 dummy;
spin_unlock(&hb1->lock);
if (hb1 != hb2)
spin_unlock(&hb2->lock);
double_unlock_hb(hb1, hb2);
#ifndef CONFIG_MMU
/*
@ -833,9 +844,7 @@ retry:
ret += op_ret;
}
spin_unlock(&hb1->lock);
if (hb1 != hb2)
spin_unlock(&hb2->lock);
double_unlock_hb(hb1, hb2);
out_put_keys:
put_futex_key(fshared, &key2);
out_put_key1:
@ -876,9 +885,7 @@ retry:
ret = get_futex_value_locked(&curval, uaddr1);
if (unlikely(ret)) {
spin_unlock(&hb1->lock);
if (hb1 != hb2)
spin_unlock(&hb2->lock);
double_unlock_hb(hb1, hb2);
put_futex_key(fshared, &key2);
put_futex_key(fshared, &key1);
@ -925,9 +932,7 @@ retry:
}
out_unlock:
spin_unlock(&hb1->lock);
if (hb1 != hb2)
spin_unlock(&hb2->lock);
double_unlock_hb(hb1, hb2);
/* drop_futex_key_refs() must be called outside the spinlocks. */
while (--drop_count >= 0)