> -----Original Message----- > From: Colin Cross [mailto:ccross@xxxxxxxxxxx] > Sent: 2013年8月24日 3:45 > To: linux-pm@xxxxxxxxxxxxxxx > Cc: linux-kernel@xxxxxxxxxxxxxxx; Neil Zhang; Joseph Lo; > linux-tegra@xxxxxxxxxxxxxxx; Colin Cross; stable@xxxxxxxxxxxxxxx; Rafael J. > Wysocki; Daniel Lezcano > Subject: [PATCH 3/3] cpuidle: coupled: fix race condition between pokes and safe > state > > The coupled cpuidle waiting loop clears pending pokes before entering the safe > state. If a poke arrives just before the pokes are cleared, but after the while > loop condition checks, the poke will be lost and the cpu will stay in the safe state > until another interrupt arrives. This may cause the cpu that sent the poke to > spin in the ready loop with interrupts off until another cpu receives an interrupt, > and if no other cpus have interrupts routed to them it can spin forever. > > Change the return value of cpuidle_coupled_clear_pokes to return if a poke was > cleared, and move the need_resched() checks into the callers. In the waiting > loop, if a poke was cleared restart the loop to repeat the while condition checks. > > Reported-by: Neil Zhang <zhangwm@xxxxxxxxxxx> > CC: stable@xxxxxxxxxxxxxxx > Signed-off-by: Colin Cross <ccross@xxxxxxxxxxx> > --- > drivers/cpuidle/coupled.c | 20 ++++++++++++++------ > 1 file changed, 14 insertions(+), 6 deletions(-) > > diff --git a/drivers/cpuidle/coupled.c b/drivers/cpuidle/coupled.c index > bbc4ba5..c91230b 100644 > --- a/drivers/cpuidle/coupled.c > +++ b/drivers/cpuidle/coupled.c > @@ -408,19 +408,22 @@ static void cpuidle_coupled_set_done(int cpu, struct > cpuidle_coupled *coupled) > * been processed and the poke bit has been cleared. > * > * Other interrupts may also be processed while interrupts are enabled, so > - * need_resched() must be tested after turning interrupts off again to make sure > + * need_resched() must be tested after this function returns to make > + sure > * the interrupt didn't schedule work that should take the cpu out of idle. > * > - * Returns 0 if need_resched was false, -EINTR if need_resched was true. > + * Returns 0 if no poke was pending, 1 if a poke was cleared. > */ > static int cpuidle_coupled_clear_pokes(int cpu) { > + if (!cpumask_test_cpu(cpu, &cpuidle_coupled_poke_pending)) > + return 0; > + > local_irq_enable(); > while (cpumask_test_cpu(cpu, &cpuidle_coupled_poke_pending)) > cpu_relax(); > local_irq_disable(); > > - return need_resched() ? -EINTR : 0; > + return 1; > } > > static bool cpuidle_coupled_any_pokes_pending(struct cpuidle_coupled > *coupled) @@ -464,7 +467,8 @@ int cpuidle_enter_state_coupled(struct > cpuidle_device *dev, > return -EINVAL; > > while (coupled->prevent) { > - if (cpuidle_coupled_clear_pokes(dev->cpu)) { > + cpuidle_coupled_clear_pokes(dev->cpu); > + if (need_resched()) { > local_irq_enable(); > return entered_state; > } > @@ -503,7 +507,10 @@ retry: > */ > while (!cpuidle_coupled_cpus_waiting(coupled) || > !cpumask_test_cpu(dev->cpu, &cpuidle_coupled_poked)) { > - if (cpuidle_coupled_clear_pokes(dev->cpu)) { > + if (cpuidle_coupled_clear_pokes(dev->cpu)) > + continue; > + > + if (need_resched()) { > cpuidle_coupled_set_not_waiting(dev->cpu, coupled); > goto out; > } > @@ -518,7 +525,8 @@ retry: > local_irq_disable(); > } > > - if (cpuidle_coupled_clear_pokes(dev->cpu)) { > + cpuidle_coupled_clear_pokes(dev->cpu); > + if (need_resched()) { > cpuidle_coupled_set_not_waiting(dev->cpu, coupled); > goto out; > } > -- > 1.8.3 I think this patch should also be workable. Thanks. Reviewed-by: Neil Zhang <zhangwm@xxxxxxxxxxx> Best Regards, Neil Zhang ?韬{.n?????%??檩??w?{.n???{炳????n?■???h?璀?｛?夸z罐?+€?zf＂?????i?????_璁?:+v??撸?
