| Message ID | 1789709.hzh3CkisvM@vostro.rjw.lan (mailing list archive) |
|---|---|
| State | RFC, archived |
| Headers | show |
On Wed, Feb 25, 2015 at 11:36:10PM +0000, Rafael J. Wysocki wrote: > On Wednesday, February 25, 2015 02:39:17 PM Lorenzo Pieralisi wrote: > > On Wed, Feb 25, 2015 at 02:13:23PM +0000, Daniel Lezcano wrote: > > > On 02/24/2015 06:58 PM, Lorenzo Pieralisi wrote: > > > > On return from cpuidle_enter_freeze() irqs are re-enabled by the function > > > > caller (ie cpuidle_idle_call) in the idle loop. This patch removes a stale > > > > local_irq_disable() call and its stale comment in cpuidle_enter_freeze(), > > > > since they disagree and do not serve a useful purpose. > > > > > > > > Cc: Rafael J. Wysocki <rjw@rjwysocki.net> > > > > Cc: Daniel Lezcano <daniel.lezcano@linaro.org> > > > > Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> > > > > --- > > > > drivers/cpuidle/cpuidle.c | 3 --- > > > > 1 file changed, 3 deletions(-) > > > > > > > > diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c > > > > index 4d53458..f47edc6c 100644 > > > > --- a/drivers/cpuidle/cpuidle.c > > > > +++ b/drivers/cpuidle/cpuidle.c > > > > @@ -144,9 +144,6 @@ void cpuidle_enter_freeze(void) > > > > cpuidle_enter(drv, dev, index); > > > > else > > > > arch_cpu_idle(); > > > > - > > > > - /* Interrupts are enabled again here. */ > > > > - local_irq_disable(); > > > > } > > > > > > Hmm, I think Rafael added this prevent lockdep to raise a warning. > > > > Ok, so the comment is there to say "at this point of execution IRQs > > are enabled", it does not refer to local_irq_disable() call effects, > > that's misleading and not necessarily nice, at least it should > > be explained. > > > > > Otherwise, cpuidle_enter or arch_cpu_idle enables the irq again and then > > > when exiting the cpu_idle_call, we enable them again, so leading to a > > > lockdep WARN in trace_hardirqs_on_caller. > > > > Would not it be better to enable irqs in cpuidle_enter_freeze() on > > returning from enter_freeze_proper() and remove the local_irq_enable() > > call in the cpuidle_idle_call() before jumping to exit_idle ? > > > > > That said, if we have to do this, it may reveal something is wrong in > > > the code. > > > > I just spotted code through inspection, I have to say at the moment it > > is not very clear what it is meant to achieve, so I put together this > > patch. > > So there are two code paths in cpuidle_idle_call(), the enter_freeze_proper() > one which does *not* re-enable interrupts and the one you modified which does > that. The local_irq_disable() is to keep things consistent. > > I'm not entirely against of re-arranging things here, but a patch like the > (untested) one below might be more appropriate. > > Rafael (who would appreciate it if people asked questions instead of sending > patches on a hunch). I understand that, I wanted to just send [patch 2], this patch was more a way to get a clarification than anything else, asking would have been more appropriate, sorry. Anyway, I did not like disabling IRQs to just re-enable them on function return, in particular the comment below seemed to apply to the following line, which is a bit misleading. /* Interrupts are enabled again here. */ local_irq_disable(); > > > --- > drivers/cpuidle/cpuidle.c | 2 +- > kernel/sched/idle.c | 1 - > 2 files changed, 1 insertion(+), 2 deletions(-) > > Index: linux-pm/drivers/cpuidle/cpuidle.c > =================================================================== > --- linux-pm.orig/drivers/cpuidle/cpuidle.c > +++ linux-pm/drivers/cpuidle/cpuidle.c > @@ -132,6 +132,7 @@ void cpuidle_enter_freeze(void) > index = cpuidle_find_deepest_state(drv, dev, true); > if (index >= 0) { > enter_freeze_proper(drv, dev, index); > + local_irq_enable(); > return; > } > > @@ -146,7 +147,6 @@ void cpuidle_enter_freeze(void) > arch_cpu_idle(); > > /* Interrupts are enabled again here. */ > - local_irq_disable(); > } > > /** > Index: linux-pm/kernel/sched/idle.c > =================================================================== > --- linux-pm.orig/kernel/sched/idle.c > +++ linux-pm/kernel/sched/idle.c > @@ -116,7 +116,6 @@ static void cpuidle_idle_call(void) > */ > if (idle_should_freeze()) { > cpuidle_enter_freeze(); > - local_irq_enable(); > goto exit_idle; > } > It looks fine, I will test it. I would add a comment to cpuidle_enter_freeze() to document it must return with IRQs enabled. Thanks, Lorenzo -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, Feb 26, 2015 at 10:48 AM, Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> wrote: > On Wed, Feb 25, 2015 at 11:36:10PM +0000, Rafael J. Wysocki wrote: >> On Wednesday, February 25, 2015 02:39:17 PM Lorenzo Pieralisi wrote: >> > On Wed, Feb 25, 2015 at 02:13:23PM +0000, Daniel Lezcano wrote: [cut] >> I'm not entirely against of re-arranging things here, but a patch like the >> (untested) one below might be more appropriate. >> >> Rafael (who would appreciate it if people asked questions instead of sending >> patches on a hunch). > > I understand that, I wanted to just send [patch 2], this patch was more > a way to get a clarification than anything else, asking would have been more > appropriate, sorry. > > Anyway, I did not like disabling IRQs to just re-enable them on function > return, in particular the comment below seemed to apply to the following > line, which is a bit misleading. I see. > > /* Interrupts are enabled again here. */ > local_irq_disable(); > >> >> >> --- >> drivers/cpuidle/cpuidle.c | 2 +- >> kernel/sched/idle.c | 1 - >> 2 files changed, 1 insertion(+), 2 deletions(-) >> >> Index: linux-pm/drivers/cpuidle/cpuidle.c >> =================================================================== >> --- linux-pm.orig/drivers/cpuidle/cpuidle.c >> +++ linux-pm/drivers/cpuidle/cpuidle.c >> @@ -132,6 +132,7 @@ void cpuidle_enter_freeze(void) >> index = cpuidle_find_deepest_state(drv, dev, true); >> if (index >= 0) { >> enter_freeze_proper(drv, dev, index); >> + local_irq_enable(); >> return; >> } >> >> @@ -146,7 +147,6 @@ void cpuidle_enter_freeze(void) >> arch_cpu_idle(); >> >> /* Interrupts are enabled again here. */ >> - local_irq_disable(); >> } >> >> /** >> Index: linux-pm/kernel/sched/idle.c >> =================================================================== >> --- linux-pm.orig/kernel/sched/idle.c >> +++ linux-pm/kernel/sched/idle.c >> @@ -116,7 +116,6 @@ static void cpuidle_idle_call(void) >> */ >> if (idle_should_freeze()) { >> cpuidle_enter_freeze(); >> - local_irq_enable(); >> goto exit_idle; >> } >> > > It looks fine, I will test it. I would add a comment to > cpuidle_enter_freeze() to document it must return with IRQs > enabled. OK Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Index: linux-pm/drivers/cpuidle/cpuidle.c =================================================================== --- linux-pm.orig/drivers/cpuidle/cpuidle.c +++ linux-pm/drivers/cpuidle/cpuidle.c @@ -132,6 +132,7 @@ void cpuidle_enter_freeze(void) index = cpuidle_find_deepest_state(drv, dev, true); if (index >= 0) { enter_freeze_proper(drv, dev, index); + local_irq_enable(); return; } @@ -146,7 +147,6 @@ void cpuidle_enter_freeze(void) arch_cpu_idle(); /* Interrupts are enabled again here. */ - local_irq_disable(); } /** Index: linux-pm/kernel/sched/idle.c =================================================================== --- linux-pm.orig/kernel/sched/idle.c +++ linux-pm/kernel/sched/idle.c @@ -116,7 +116,6 @@ static void cpuidle_idle_call(void) */ if (idle_should_freeze()) { cpuidle_enter_freeze(); - local_irq_enable(); goto exit_idle; }