* [PATCH arm 0/2] Fixes for ARM use of scheduler when offline @ 2015-04-23 20:06 Paul E. McKenney 2015-04-23 20:07 ` [PATCH arm 1/2] arm64: Use common outgoing-CPU-notification code Paul E. McKenney 0 siblings, 1 reply; 7+ messages in thread From: Paul E. McKenney @ 2015-04-23 20:06 UTC (permalink / raw) To: linux-arm-kernel Hello! This series is strictly FYI. I am simply sending it as a heads-up. The diagnostics surrounding using RCU from an offline CPU will be tightening up, which might cause splats to come my way. If such splats do come my way, I will reply with the patches in this series. I know you guys have been working to put something better together, which is great -- just letting you know of fallback patches, when and if. If you would like to push these up your tree or ack them and have me push them, that is of course fine as well. The first patch in the series does arm64, and the second does arm. Thanx, Paul ------------------------------------------------------------------------ b/arch/arm/kernel/smp.c | 6 ++---- b/arch/arm64/kernel/smp.c | 6 ++---- 2 files changed, 4 insertions(+), 8 deletions(-) ^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH arm 1/2] arm64: Use common outgoing-CPU-notification code 2015-04-23 20:06 [PATCH arm 0/2] Fixes for ARM use of scheduler when offline Paul E. McKenney @ 2015-04-23 20:07 ` Paul E. McKenney 2015-04-23 20:07 ` [PATCH arm 2/2] arm: " Paul E. McKenney 2015-04-30 9:50 ` [PATCH arm 1/2] arm64: " Catalin Marinas 0 siblings, 2 replies; 7+ messages in thread From: Paul E. McKenney @ 2015-04-23 20:07 UTC (permalink / raw) To: linux-arm-kernel From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> This commit removes the open-coded CPU-offline notification with new common code. In particular, this change avoids calling scheduler code using RCU from an offline CPU that RCU is ignoring. This is a minimal change. A more intrusive change might invoke the cpu_check_up_prepare() and cpu_set_state_online() functions at CPU-online time, which would allow onlining throw an error if the CPU did not go offline properly. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: linux-arm-kernel at lists.infradead.org Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> --- arch/arm64/kernel/smp.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c index 328b8ce4b007..6dc727a6e73e 100644 --- a/arch/arm64/kernel/smp.c +++ b/arch/arm64/kernel/smp.c @@ -252,15 +252,13 @@ static int op_cpu_kill(unsigned int cpu) return cpu_ops[cpu]->cpu_kill(cpu); } -static DECLARE_COMPLETION(cpu_died); - /* * called on the thread which is asking for a CPU to be shutdown - * waits until shutdown has completed, or it is timed out. */ void __cpu_die(unsigned int cpu) { - if (!wait_for_completion_timeout(&cpu_died, msecs_to_jiffies(5000))) { + if (!cpu_wait_death(cpu, 5)) { pr_crit("CPU%u: cpu didn't die\n", cpu); return; } @@ -293,7 +291,7 @@ void cpu_die(void) local_irq_disable(); /* Tell __cpu_die() that this CPU is now safe to dispose of */ - complete(&cpu_died); + (void)cpu_report_death(); /* * Actually shutdown the CPU. This must never fail. The specific hotplug -- 1.8.1.5 ^ permalink raw reply related [flat|nested] 7+ messages in thread
* [PATCH arm 2/2] arm: Use common outgoing-CPU-notification code 2015-04-23 20:07 ` [PATCH arm 1/2] arm64: Use common outgoing-CPU-notification code Paul E. McKenney @ 2015-04-23 20:07 ` Paul E. McKenney 2015-04-30 9:50 ` [PATCH arm 1/2] arm64: " Catalin Marinas 1 sibling, 0 replies; 7+ messages in thread From: Paul E. McKenney @ 2015-04-23 20:07 UTC (permalink / raw) To: linux-arm-kernel From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> This commit removes the open-coded CPU-offline notification with new common code. In particular, this change avoids calling scheduler code using RCU from an offline CPU that RCU is ignoring. This is a minimal change. A more intrusive change might invoke the cpu_check_up_prepare() and cpu_set_state_online() functions at CPU-online time, which would allow onlining throw an error if the CPU did not go offline properly. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: linux-arm-kernel at lists.infradead.org Cc: Russell King <linux@arm.linux.org.uk> --- arch/arm/kernel/smp.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c index 86ef244c5a24..de309f431463 100644 --- a/arch/arm/kernel/smp.c +++ b/arch/arm/kernel/smp.c @@ -213,15 +213,13 @@ int __cpu_disable(void) return 0; } -static DECLARE_COMPLETION(cpu_died); - /* * called on the thread which is asking for a CPU to be shutdown - * waits until shutdown has completed, or it is timed out. */ void __cpu_die(unsigned int cpu) { - if (!wait_for_completion_timeout(&cpu_died, msecs_to_jiffies(5000))) { + if (!cpu_wait_death(cpu, 5)) { pr_err("CPU%u: cpu didn't die\n", cpu); return; } @@ -267,7 +265,7 @@ void __ref cpu_die(void) * this returns, power and/or clocks can be removed at any point * from this CPU and its cache by platform_cpu_kill(). */ - complete(&cpu_died); + (void)cpu_report_death(); /* * Ensure that the cache lines associated with that completion are -- 1.8.1.5 ^ permalink raw reply related [flat|nested] 7+ messages in thread
* [PATCH arm 1/2] arm64: Use common outgoing-CPU-notification code 2015-04-23 20:07 ` [PATCH arm 1/2] arm64: Use common outgoing-CPU-notification code Paul E. McKenney 2015-04-23 20:07 ` [PATCH arm 2/2] arm: " Paul E. McKenney @ 2015-04-30 9:50 ` Catalin Marinas 2015-05-01 15:08 ` Paul E. McKenney 1 sibling, 1 reply; 7+ messages in thread From: Catalin Marinas @ 2015-04-30 9:50 UTC (permalink / raw) To: linux-arm-kernel Hi Paul, On Thu, Apr 23, 2015 at 01:07:33PM -0700, Paul E. McKenney wrote: > diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c > index 328b8ce4b007..6dc727a6e73e 100644 > --- a/arch/arm64/kernel/smp.c > +++ b/arch/arm64/kernel/smp.c > @@ -252,15 +252,13 @@ static int op_cpu_kill(unsigned int cpu) > return cpu_ops[cpu]->cpu_kill(cpu); > } > > -static DECLARE_COMPLETION(cpu_died); > - > /* > * called on the thread which is asking for a CPU to be shutdown - > * waits until shutdown has completed, or it is timed out. > */ > void __cpu_die(unsigned int cpu) > { > - if (!wait_for_completion_timeout(&cpu_died, msecs_to_jiffies(5000))) { > + if (!cpu_wait_death(cpu, 5)) { > pr_crit("CPU%u: cpu didn't die\n", cpu); > return; > } > @@ -293,7 +291,7 @@ void cpu_die(void) > local_irq_disable(); > > /* Tell __cpu_die() that this CPU is now safe to dispose of */ > - complete(&cpu_died); > + (void)cpu_report_death(); > > /* > * Actually shutdown the CPU. This must never fail. The specific hotplug Are these functions are only defined when HOTPLUG_CPU is enabled? On arm64 we can end up with this option disabled if SUSPEND is disabled. -- Catalin ^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH arm 1/2] arm64: Use common outgoing-CPU-notification code 2015-04-30 9:50 ` [PATCH arm 1/2] arm64: " Catalin Marinas @ 2015-05-01 15:08 ` Paul E. McKenney 2015-05-01 16:29 ` Catalin Marinas 0 siblings, 1 reply; 7+ messages in thread From: Paul E. McKenney @ 2015-05-01 15:08 UTC (permalink / raw) To: linux-arm-kernel On Thu, Apr 30, 2015 at 10:50:55AM +0100, Catalin Marinas wrote: > Hi Paul, > > On Thu, Apr 23, 2015 at 01:07:33PM -0700, Paul E. McKenney wrote: > > diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c > > index 328b8ce4b007..6dc727a6e73e 100644 > > --- a/arch/arm64/kernel/smp.c > > +++ b/arch/arm64/kernel/smp.c > > @@ -252,15 +252,13 @@ static int op_cpu_kill(unsigned int cpu) > > return cpu_ops[cpu]->cpu_kill(cpu); > > } > > > > -static DECLARE_COMPLETION(cpu_died); > > - > > /* > > * called on the thread which is asking for a CPU to be shutdown - > > * waits until shutdown has completed, or it is timed out. > > */ > > void __cpu_die(unsigned int cpu) > > { > > - if (!wait_for_completion_timeout(&cpu_died, msecs_to_jiffies(5000))) { > > + if (!cpu_wait_death(cpu, 5)) { > > pr_crit("CPU%u: cpu didn't die\n", cpu); > > return; > > } > > @@ -293,7 +291,7 @@ void cpu_die(void) > > local_irq_disable(); > > > > /* Tell __cpu_die() that this CPU is now safe to dispose of */ > > - complete(&cpu_died); > > + (void)cpu_report_death(); > > > > /* > > * Actually shutdown the CPU. This must never fail. The specific hotplug > > Are these functions are only defined when HOTPLUG_CPU is enabled? On > arm64 we can end up with this option disabled if SUSPEND is disabled. Yep, only with HOTPLUG_CPU. And yes, both SUSPEND and HIBERNATION can force HOTPLUG_CPU, so if you have neiter SUSPEND nor HIBERNATION, you won't have HOTPLUG_CPU. This -should- be OK, because you should also not have __cpu_die() if !HOTPLUG_CPU. Or am I missing your point? Thanx, Paul ^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH arm 1/2] arm64: Use common outgoing-CPU-notification code 2015-05-01 15:08 ` Paul E. McKenney @ 2015-05-01 16:29 ` Catalin Marinas 2015-05-01 19:18 ` Paul E. McKenney 0 siblings, 1 reply; 7+ messages in thread From: Catalin Marinas @ 2015-05-01 16:29 UTC (permalink / raw) To: linux-arm-kernel On Fri, May 01, 2015 at 08:08:48AM -0700, Paul E. McKenney wrote: > On Thu, Apr 30, 2015 at 10:50:55AM +0100, Catalin Marinas wrote: > > On Thu, Apr 23, 2015 at 01:07:33PM -0700, Paul E. McKenney wrote: > > > diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c > > > index 328b8ce4b007..6dc727a6e73e 100644 > > > --- a/arch/arm64/kernel/smp.c > > > +++ b/arch/arm64/kernel/smp.c > > > @@ -252,15 +252,13 @@ static int op_cpu_kill(unsigned int cpu) > > > return cpu_ops[cpu]->cpu_kill(cpu); > > > } > > > > > > -static DECLARE_COMPLETION(cpu_died); > > > - > > > /* > > > * called on the thread which is asking for a CPU to be shutdown - > > > * waits until shutdown has completed, or it is timed out. > > > */ > > > void __cpu_die(unsigned int cpu) > > > { > > > - if (!wait_for_completion_timeout(&cpu_died, msecs_to_jiffies(5000))) { > > > + if (!cpu_wait_death(cpu, 5)) { > > > pr_crit("CPU%u: cpu didn't die\n", cpu); > > > return; > > > } > > > @@ -293,7 +291,7 @@ void cpu_die(void) > > > local_irq_disable(); > > > > > > /* Tell __cpu_die() that this CPU is now safe to dispose of */ > > > - complete(&cpu_died); > > > + (void)cpu_report_death(); > > > > > > /* > > > * Actually shutdown the CPU. This must never fail. The specific hotplug > > > > Are these functions are only defined when HOTPLUG_CPU is enabled? On > > arm64 we can end up with this option disabled if SUSPEND is disabled. > > Yep, only with HOTPLUG_CPU. And yes, both SUSPEND and HIBERNATION can > force HOTPLUG_CPU, so if you have neiter SUSPEND nor HIBERNATION, you > won't have HOTPLUG_CPU. This -should- be OK, because you should also > not have __cpu_die() if !HOTPLUG_CPU. Ah, you are right. I got myself confused. So is this patch ready for upstreaming or just for our information? -- Catalin ^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH arm 1/2] arm64: Use common outgoing-CPU-notification code 2015-05-01 16:29 ` Catalin Marinas @ 2015-05-01 19:18 ` Paul E. McKenney 0 siblings, 0 replies; 7+ messages in thread From: Paul E. McKenney @ 2015-05-01 19:18 UTC (permalink / raw) To: linux-arm-kernel On Fri, May 01, 2015 at 05:29:15PM +0100, Catalin Marinas wrote: > On Fri, May 01, 2015 at 08:08:48AM -0700, Paul E. McKenney wrote: > > On Thu, Apr 30, 2015 at 10:50:55AM +0100, Catalin Marinas wrote: > > > On Thu, Apr 23, 2015 at 01:07:33PM -0700, Paul E. McKenney wrote: > > > > diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c > > > > index 328b8ce4b007..6dc727a6e73e 100644 > > > > --- a/arch/arm64/kernel/smp.c > > > > +++ b/arch/arm64/kernel/smp.c > > > > @@ -252,15 +252,13 @@ static int op_cpu_kill(unsigned int cpu) > > > > return cpu_ops[cpu]->cpu_kill(cpu); > > > > } > > > > > > > > -static DECLARE_COMPLETION(cpu_died); > > > > - > > > > /* > > > > * called on the thread which is asking for a CPU to be shutdown - > > > > * waits until shutdown has completed, or it is timed out. > > > > */ > > > > void __cpu_die(unsigned int cpu) > > > > { > > > > - if (!wait_for_completion_timeout(&cpu_died, msecs_to_jiffies(5000))) { > > > > + if (!cpu_wait_death(cpu, 5)) { > > > > pr_crit("CPU%u: cpu didn't die\n", cpu); > > > > return; > > > > } > > > > @@ -293,7 +291,7 @@ void cpu_die(void) > > > > local_irq_disable(); > > > > > > > > /* Tell __cpu_die() that this CPU is now safe to dispose of */ > > > > - complete(&cpu_died); > > > > + (void)cpu_report_death(); > > > > > > > > /* > > > > * Actually shutdown the CPU. This must never fail. The specific hotplug > > > > > > Are these functions are only defined when HOTPLUG_CPU is enabled? On > > > arm64 we can end up with this option disabled if SUSPEND is disabled. > > > > Yep, only with HOTPLUG_CPU. And yes, both SUSPEND and HIBERNATION can > > force HOTPLUG_CPU, so if you have neiter SUSPEND nor HIBERNATION, you > > won't have HOTPLUG_CPU. This -should- be OK, because you should also > > not have __cpu_die() if !HOTPLUG_CPU. > > Ah, you are right. I got myself confused. > > So is this patch ready for upstreaming or just for our information? It does need some testing, and I don't have access to an arm64 system. That said, very similar patches have worked for other architectures. So if it works on one of your systems, it should be ready to go upstream. Which would be better than me sending it individually to people who run into the new more-strict diagnostics. ;-) Thanx, Paul ^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2015-05-01 19:18 UTC | newest] Thread overview: 7+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2015-04-23 20:06 [PATCH arm 0/2] Fixes for ARM use of scheduler when offline Paul E. McKenney 2015-04-23 20:07 ` [PATCH arm 1/2] arm64: Use common outgoing-CPU-notification code Paul E. McKenney 2015-04-23 20:07 ` [PATCH arm 2/2] arm: " Paul E. McKenney 2015-04-30 9:50 ` [PATCH arm 1/2] arm64: " Catalin Marinas 2015-05-01 15:08 ` Paul E. McKenney 2015-05-01 16:29 ` Catalin Marinas 2015-05-01 19:18 ` Paul E. McKenney
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