Messages in this thread |  | | | Date | Fri, 10 Jul 2009 20:08:03 +0200 | | From | Frederic Weisbecker <> | | Subject | Re: [PATCH] sched: Move the sleeping while atomic checks early in cond_resched() |
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On Fri, Jul 10, 2009 at 07:43:30PM +0200, Peter Zijlstra wrote: > On Fri, 2009-07-10 at 19:14 +0200, Frederic Weisbecker wrote: > > might_sleep() is called lately in cond_resched(), after the > > need_resched()/preempt enabled/system running tests are checked. > > > > It's better to check the sleeps while atomic earlier and not depend > > on some environment datas that reduce the chances to detect a > > problem. > > > > Changes in v2: > > - call __might_sleep() directly instead of might_sleep() which may call > > cond_resched() > > - turn cond_resched() into a macro so that the file:line couple reported > > refers to the caller of cond_resched() and not __cond_resched() itself. > > - drop the obsolete CONFIG_PREEMPT_BKL related zones > > > > Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> > > Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> > > > > Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> > > --- > > include/linux/sched.h | 22 +++++++--------------- > > kernel/sched.c | 5 ++--- > > 2 files changed, 9 insertions(+), 18 deletions(-) > > > > diff --git a/include/linux/sched.h b/include/linux/sched.h > > index 0cb0d8d..737f569 100644 > > --- a/include/linux/sched.h > > +++ b/include/linux/sched.h > > @@ -2276,23 +2276,15 @@ static inline int need_resched(void) > > * cond_resched_softirq() will enable bhs before scheduling. > > */ > > extern int _cond_resched(void); > > -#ifdef CONFIG_PREEMPT_BKL > > -static inline int cond_resched(void) > > -{ > > - return 0; > > -} > > -#else > > -static inline int cond_resched(void) > > -{ > > - return _cond_resched(); > > -} > > -#endif > > +#define cond_resched() ({ \ > > + __might_sleep(__FILE__, __LINE__); \ > > + _cond_resched(); \ > > +}) > > I don't think this will compile for !CONFIG_DEBUG_SPINLOCK_SLEEP.
Ahh, right.
> > extern int cond_resched_lock(spinlock_t * lock); > > extern int cond_resched_softirq(void); > > -static inline int cond_resched_bkl(void) > > -{ > > - return _cond_resched(); > > -} > > + > > +#define cond_resched_bkl() cond_resched(); > > We might as well convert the one user of this ;-)
Ok :)
> > /* > > * Does a critical section need to be broken due to another > > diff --git a/kernel/sched.c b/kernel/sched.c > > index 87ecac1..649ec92 100644 > > --- a/kernel/sched.c > > +++ b/kernel/sched.c > > @@ -6605,9 +6605,6 @@ SYSCALL_DEFINE0(sched_yield) > > > > static void __cond_resched(void) > > { > > -#ifdef CONFIG_DEBUG_SPINLOCK_SLEEP > > - __might_sleep(__FILE__, __LINE__); > > -#endif > > /* > > * The BKS might be reacquired before we have dropped > > * PREEMPT_ACTIVE, which could trigger a second > > @@ -6644,6 +6641,7 @@ int cond_resched_lock(spinlock_t *lock) > > > > if (spin_needbreak(lock) || resched) { > > spin_unlock(lock); > > + __might_sleep(__FILE__, __LINE__); > > if (resched && need_resched()) > > __cond_resched(); > > else > > @@ -6661,6 +6659,7 @@ int __sched cond_resched_softirq(void) > > > > if (need_resched() && system_state == SYSTEM_RUNNING) { > > local_bh_enable(); > > + __might_sleep(__FILE__, __LINE__); > > __cond_resched(); > > local_bh_disable(); > > return 1; > > Right, how about renaming these to _cond_resched_{lock,softirq}, and > added a __might_sleep() definition for !DEBUG_SPINLOCK_SLEEP and add > macro wrappers to sched.c for these two as well?
I did that first but thought that might_sleep() would fail in a spinlock held or softirq context, right?
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