pushdown of migrate_disable/enable from write_*lock* to the rt_write_*lock*
api level
general mapping of write_*lock* to mutexes:
write_*lock*
`-> rt_write_*lock*
`-> __spin_lock (the sleeping __spin_lock)
`-> rt_mutex
write_*lock*s are non-recursive so we have two lock chains to consider
- write_trylock*/write_unlock
- write_lock*/wirte_unlock
for both paths the migration_disable/enable must be balanced.
write_trylock* mapping:
write_trylock_irqsave
`-> rt_write_trylock_irqsave
write_trylock \
`--------> rt_write_trylock
ret = rt_mutex_trylock
rt_mutex_fasttrylock
rt_mutex_cmpxchg
if (ret)
migrate_disable
write_lock* mapping:
write_lock_irqsave
`-> rt_write_lock_irqsave
write_lock_irq -> write_lock ----. \
write_lock_bh -+ \
`-> rt_write_lock
__rt_spin_lock()
rt_spin_lock_fastlock()
rt_mutex_cmpxchg()
migrate_disable()
write_unlock* mapping:
write_unlock_irqrestore.
write_unlock_bh -------+
write_unlock_irq -> write_unlock ----------+
`-> rt_write_unlock()
__rt_spin_unlock()
rt_spin_lock_fastunlock()
rt_mutex_cmpxchg()
migrate_enable()
So calls to migrate_disable/enable() are better placed at the rt_write_*
level of lock/trylock/unlock as all of the write_*lock* API has this as a
common path.
This approach to write_*_bh also eliminates the concerns raised with
regards to api inbalances (write_lock_bh -> write_unlock+local_bh_enable)
this is on top of 3.12.6-rt9 with
timers-do-not-raise-softirq-unconditionally.patch removed
No change of functional behavior
Tested-by: Carsten Emde <c.e...@osadl.org>
Signed-off-by: Nicholas Mc Guire <der.h...@hofr.at>
---
include/linux/rwlock_rt.h | 6 ------
kernel/rt.c | 4 ++--
2 files changed, 2 insertions(+), 8 deletions(-)
diff --git a/include/linux/rwlock_rt.h b/include/linux/rwlock_rt.h
index 853ee36..a276fae 100644
--- a/include/linux/rwlock_rt.h
+++ b/include/linux/rwlock_rt.h
@@ -40,7 +40,6 @@ extern void __rt_rwlock_init(rwlock_t *rwlock, char *name,
struct lock_class_key
#define write_lock_irqsave(lock, flags) \
do { \
typecheck(unsigned long, flags); \
- migrate_disable(); \
flags = rt_write_lock_irqsave(lock); \
} while (0)
@@ -61,14 +60,12 @@ extern void __rt_rwlock_init(rwlock_t *rwlock, char *name,
struct lock_class_key
#define write_lock(lock) \
do { \
- migrate_disable(); \
rt_write_lock(lock); \
} while (0)
#define write_lock_bh(lock) \
do { \
local_bh_disable(); \
- migrate_disable(); \
rt_write_lock(lock); \
} while (0)
@@ -92,13 +89,11 @@ extern void __rt_rwlock_init(rwlock_t *rwlock, char *name,
struct lock_class_key
#define write_unlock(lock) \
do { \
rt_write_unlock(lock); \
- migrate_enable(); \
} while (0)
#define write_unlock_bh(lock) \
do { \
rt_write_unlock(lock); \
- migrate_enable(); \
local_bh_enable(); \
} while (0)
@@ -117,7 +112,6 @@ extern void __rt_rwlock_init(rwlock_t *rwlock, char *name,
struct lock_class_key
typecheck(unsigned long, flags); \
(void) flags; \
rt_write_unlock(lock); \
- migrate_enable(); \
} while (0)
#endif
diff --git a/kernel/rt.c b/kernel/rt.c
index 29771e2..c43c923 100644
--- a/kernel/rt.c
+++ b/kernel/rt.c
@@ -197,8 +197,6 @@ int __lockfunc rt_write_trylock_irqsave(rwlock_t *rwlock,
unsigned long *flags)
*flags = 0;
ret = rt_write_trylock(rwlock);
- if (ret)
- migrate_disable();
return ret;
}
EXPORT_SYMBOL(rt_write_trylock_irqsave);
@@ -234,6 +232,7 @@ EXPORT_SYMBOL(rt_read_trylock);
void __lockfunc rt_write_lock(rwlock_t *rwlock)
{
rwlock_acquire(&rwlock->dep_map, 0, 0, _RET_IP_);
+ migrate_disable();
__rt_spin_lock(&rwlock->lock);
}
EXPORT_SYMBOL(rt_write_lock);
@@ -259,6 +258,7 @@ void __lockfunc rt_write_unlock(rwlock_t *rwlock)
/* NOTE: we always pass in '1' for nested, for simplicity */
rwlock_release(&rwlock->dep_map, 1, _RET_IP_);
__rt_spin_unlock(&rwlock->lock);
+ migrate_enable();
}
EXPORT_SYMBOL(rt_write_unlock);
--
1.7.2.5
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
