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Date: Sat, 26 Apr 2014 15:58:19 +0200
From: Mike Galbraith <umgwanakikbuti@...il.com>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: linux-rt-users <linux-rt-users@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>,
Thomas Gleixner <tglx@...utronix.de>, rostedt@...dmis.org,
John Kacur <jkacur@...hat.com>
Subject: Re: [ANNOUNCE] 3.14-rt1
On Sat, 2014-04-26 at 10:38 +0200, Mike Galbraith wrote:
> On Fri, 2014-04-25 at 09:40 +0200, Mike Galbraith wrote:
>
> > Hotplug can still deadlock in rt trees too, and will if you beat it
> > hard.
>
> Box actually deadlocks like so.
...
3.12-rt looks a bit busted migrate_disable/enable() wise.
/me eyeballs 3.10-rt (looks better), confirms 3.10-rt hotplug works,
swipes working code, confirms 3.12-rt now works. Yup, that was it.
When I fix lg_global_lock() (I think it and Medusa are both busted) I
bet a nickle 3.14-rt will work.
Hm, actually, rt_write_trylock() in swiped 3.10-rt code below (and some
others) look busted to me. migrate_disable() _after_ grabbing a lock is
too late, no?
---
include/linux/rwlock_rt.h | 32 ++++++++++++++++++++++++++++----
kernel/rt.c | 21 +++++++++++----------
2 files changed, 39 insertions(+), 14 deletions(-)
--- a/include/linux/rwlock_rt.h
+++ b/include/linux/rwlock_rt.h
@@ -33,50 +33,72 @@ extern void __rt_rwlock_init(rwlock_t *r
#define read_lock_irqsave(lock, flags) \
do { \
typecheck(unsigned long, flags); \
+ migrate_disable(); \
flags = rt_read_lock_irqsave(lock); \
} while (0)
#define write_lock_irqsave(lock, flags) \
do { \
typecheck(unsigned long, flags); \
+ migrate_disable(); \
flags = rt_write_lock_irqsave(lock); \
} while (0)
-#define read_lock(lock) rt_read_lock(lock)
+#define read_lock(lock) \
+ do { \
+ migrate_disable(); \
+ rt_read_lock(lock); \
+ } while (0)
#define read_lock_bh(lock) \
do { \
local_bh_disable(); \
+ migrate_disable(); \
rt_read_lock(lock); \
} while (0)
#define read_lock_irq(lock) read_lock(lock)
-#define write_lock(lock) rt_write_lock(lock)
+#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)
#define write_lock_irq(lock) write_lock(lock)
-#define read_unlock(lock) rt_read_unlock(lock)
+#define read_unlock(lock) \
+ do { \
+ rt_read_unlock(lock); \
+ migrate_enable(); \
+ } while (0)
#define read_unlock_bh(lock) \
do { \
rt_read_unlock(lock); \
+ migrate_enable(); \
local_bh_enable(); \
} while (0)
#define read_unlock_irq(lock) read_unlock(lock)
-#define write_unlock(lock) rt_write_unlock(lock)
+#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)
@@ -87,6 +109,7 @@ extern void __rt_rwlock_init(rwlock_t *r
typecheck(unsigned long, flags); \
(void) flags; \
rt_read_unlock(lock); \
+ migrate_enable(); \
} while (0)
#define write_unlock_irqrestore(lock, flags) \
@@ -94,6 +117,7 @@ extern void __rt_rwlock_init(rwlock_t *r
typecheck(unsigned long, flags); \
(void) flags; \
rt_write_unlock(lock); \
+ migrate_enable(); \
} while (0)
#endif
--- a/kernel/rt.c
+++ b/kernel/rt.c
@@ -182,10 +182,11 @@ int __lockfunc rt_write_trylock(rwlock_t
{
int ret = rt_mutex_trylock(&rwlock->lock);
- if (ret) {
+ migrate_disable();
+ if (ret)
rwlock_acquire(&rwlock->dep_map, 0, 1, _RET_IP_);
- migrate_disable();
- }
+ else
+ migrate_enable();
return ret;
}
@@ -196,7 +197,10 @@ int __lockfunc rt_write_trylock_irqsave(
int ret;
*flags = 0;
+ migrate_disable();
ret = rt_write_trylock(rwlock);
+ if (!ret)
+ migrate_enable();
return ret;
}
EXPORT_SYMBOL(rt_write_trylock_irqsave);
@@ -211,18 +215,19 @@ int __lockfunc rt_read_trylock(rwlock_t
* but not when read_depth == 0 which means that the lock is
* write locked.
*/
+ migrate_disable();
if (rt_mutex_owner(lock) != current) {
ret = rt_mutex_trylock(lock);
- if (ret) {
+ if (ret)
rwlock_acquire(&rwlock->dep_map, 0, 1, _RET_IP_);
- migrate_disable();
- }
} else if (!rwlock->read_depth) {
ret = 0;
}
if (ret)
rwlock->read_depth++;
+ else
+ migrate_enable();
return ret;
}
@@ -231,7 +236,6 @@ 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);
@@ -246,7 +250,6 @@ void __lockfunc rt_read_lock(rwlock_t *r
if (rt_mutex_owner(lock) != current) {
rwlock_acquire(&rwlock->dep_map, 0, 0, _RET_IP_);
__rt_spin_lock(lock);
- migrate_disable();
}
rwlock->read_depth++;
}
@@ -258,7 +261,6 @@ void __lockfunc rt_write_unlock(rwlock_t
/* 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);
@@ -268,7 +270,6 @@ void __lockfunc rt_read_unlock(rwlock_t
if (--rwlock->read_depth == 0) {
rwlock_release(&rwlock->dep_map, 1, _RET_IP_);
__rt_spin_unlock(&rwlock->lock);
- migrate_enable();
}
}
EXPORT_SYMBOL(rt_read_unlock);
--
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