* [PATCH tip/core/rcu 7/9] arm64: Use common outgoing-CPU-notification code [not found] ` <1431467407-1223-1-git-send-email-paulmck@linux.vnet.ibm.com> @ 2015-05-12 21:50 ` Paul E. McKenney 2015-05-21 8:58 ` Will Deacon 2015-05-12 21:50 ` [PATCH tip/core/rcu 8/9] arm: " Paul E. McKenney 1 sibling, 1 reply; 7+ messages in thread From: Paul E. McKenney @ 2015-05-12 21:50 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 2cb008177252..a899c1beff54 100644 --- a/arch/arm64/kernel/smp.c +++ b/arch/arm64/kernel/smp.c @@ -253,15 +253,13 @@ 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; } @@ -294,7 +292,7 @@ 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 tip/core/rcu 7/9] arm64: Use common outgoing-CPU-notification code 2015-05-12 21:50 ` [PATCH tip/core/rcu 7/9] arm64: Use common outgoing-CPU-notification code Paul E. McKenney @ 2015-05-21 8:58 ` Will Deacon 2015-05-21 12:48 ` Paul E. McKenney 0 siblings, 1 reply; 7+ messages in thread From: Will Deacon @ 2015-05-21 8:58 UTC (permalink / raw) To: linux-arm-kernel Hi Paul, Sorry for being late on this one. On Tue, May 12, 2015 at 10:50:05PM +0100, Paul E. McKenney wrote: > 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(-) I don't have a better idea, so: Acked-by: Will Deacon <will.deacon@arm.com> Is this queued via -tip already, or can we pick it into the arm64 tree for 4.2? Cheers, Will > diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c > index 2cb008177252..a899c1beff54 100644 > --- a/arch/arm64/kernel/smp.c > +++ b/arch/arm64/kernel/smp.c > @@ -253,15 +253,13 @@ 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; > } > @@ -294,7 +292,7 @@ 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 [flat|nested] 7+ messages in thread
* [PATCH tip/core/rcu 7/9] arm64: Use common outgoing-CPU-notification code 2015-05-21 8:58 ` Will Deacon @ 2015-05-21 12:48 ` Paul E. McKenney 2015-05-21 13:25 ` Catalin Marinas 0 siblings, 1 reply; 7+ messages in thread From: Paul E. McKenney @ 2015-05-21 12:48 UTC (permalink / raw) To: linux-arm-kernel On Thu, May 21, 2015 at 09:58:06AM +0100, Will Deacon wrote: > Hi Paul, > > Sorry for being late on this one. No problem! In fact, just in time -- I was going to bug you about this later today. ;-) > On Tue, May 12, 2015 at 10:50:05PM +0100, Paul E. McKenney wrote: > > 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(-) > > I don't have a better idea, so: > > Acked-by: Will Deacon <will.deacon@arm.com> > > Is this queued via -tip already, or can we pick it into the arm64 tree > for 4.2? Feel free to take it into the arm64 tree. Just let me know, and I will drop it from my tree. Now I only need to bug the arm32 guys. ;-) Thanx, Paul > Cheers, > > Will > > > diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c > > index 2cb008177252..a899c1beff54 100644 > > --- a/arch/arm64/kernel/smp.c > > +++ b/arch/arm64/kernel/smp.c > > @@ -253,15 +253,13 @@ 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; > > } > > @@ -294,7 +292,7 @@ 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 [flat|nested] 7+ messages in thread
* [PATCH tip/core/rcu 7/9] arm64: Use common outgoing-CPU-notification code 2015-05-21 12:48 ` Paul E. McKenney @ 2015-05-21 13:25 ` Catalin Marinas 2015-05-22 3:26 ` Paul E. McKenney 0 siblings, 1 reply; 7+ messages in thread From: Catalin Marinas @ 2015-05-21 13:25 UTC (permalink / raw) To: linux-arm-kernel On Thu, May 21, 2015 at 05:48:33AM -0700, Paul E. McKenney wrote: > On Thu, May 21, 2015 at 09:58:06AM +0100, Will Deacon wrote: > > On Tue, May 12, 2015 at 10:50:05PM +0100, Paul E. McKenney wrote: > > > 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(-) > > > > I don't have a better idea, so: > > > > Acked-by: Will Deacon <will.deacon@arm.com> > > > > Is this queued via -tip already, or can we pick it into the arm64 tree > > for 4.2? > > Feel free to take it into the arm64 tree. Just let me know, and I > will drop it from my tree. Queued for 4.2. Thanks. -- Catalin ^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH tip/core/rcu 7/9] arm64: Use common outgoing-CPU-notification code 2015-05-21 13:25 ` Catalin Marinas @ 2015-05-22 3:26 ` Paul E. McKenney 0 siblings, 0 replies; 7+ messages in thread From: Paul E. McKenney @ 2015-05-22 3:26 UTC (permalink / raw) To: linux-arm-kernel On Thu, May 21, 2015 at 02:25:57PM +0100, Catalin Marinas wrote: > On Thu, May 21, 2015 at 05:48:33AM -0700, Paul E. McKenney wrote: > > On Thu, May 21, 2015 at 09:58:06AM +0100, Will Deacon wrote: > > > On Tue, May 12, 2015 at 10:50:05PM +0100, Paul E. McKenney wrote: > > > > 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(-) > > > > > > I don't have a better idea, so: > > > > > > Acked-by: Will Deacon <will.deacon@arm.com> > > > > > > Is this queued via -tip already, or can we pick it into the arm64 tree > > > for 4.2? > > > > Feel free to take it into the arm64 tree. Just let me know, and I > > will drop it from my tree. > > Queued for 4.2. Thanks. Very good, dropped from my tree. Thanx, Paul ^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH tip/core/rcu 8/9] arm: Use common outgoing-CPU-notification code [not found] ` <1431467407-1223-1-git-send-email-paulmck@linux.vnet.ibm.com> 2015-05-12 21:50 ` [PATCH tip/core/rcu 7/9] arm64: Use common outgoing-CPU-notification code Paul E. McKenney @ 2015-05-12 21:50 ` Paul E. McKenney 2015-12-14 12:18 ` Geert Uytterhoeven 1 sibling, 1 reply; 7+ messages in thread From: Paul E. McKenney @ 2015-05-12 21:50 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 cca5b8758185..8ef0ef0287ee 100644 --- a/arch/arm/kernel/smp.c +++ b/arch/arm/kernel/smp.c @@ -218,15 +218,13 @@ 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; } @@ -272,7 +270,7 @@ 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 tip/core/rcu 8/9] arm: Use common outgoing-CPU-notification code 2015-05-12 21:50 ` [PATCH tip/core/rcu 8/9] arm: " Paul E. McKenney @ 2015-12-14 12:18 ` Geert Uytterhoeven 0 siblings, 0 replies; 7+ messages in thread From: Geert Uytterhoeven @ 2015-12-14 12:18 UTC (permalink / raw) To: linux-arm-kernel Hi Paul, On Tue, May 12, 2015 at 11:50 PM, Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote: > 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> Tested-by: Geert Uytterhoeven <geert+renesas@glider.be> Thanks, this seems to fix the intermittent "suspicious RCU usage" warnings I've been seeing during suspend to RAM on r8a7791/koelsch, which has a dual-core Cortex A15: Disabling non-boot CPUs ... =============================== [ INFO: suspicious RCU usage. ] 4.4.0-rc4-koelsch #2123 Tainted: G W ------------------------------- kernel/sched/fair.c:4938 suspicious rcu_dereference_check() usage! other info that might help us debug this: RCU used illegally from offline CPU! rcu_scheduler_active = 1, debug_locks = 0 3 locks held by swapper/1/0: #0: ((cpu_died).wait.lock){......}, at: [<c006077c>] complete+0x14/0x44 #1: (&p->pi_lock){-.-.-.}, at: [<c004b8a8>] try_to_wake_up+0x24/0x340 #2: (rcu_read_lock){......}, at: [<c0052740>] select_task_rq_fair+0xb4/0x820 stack backtrace: CPU: 1 PID: 0 Comm: swapper/1 Tainted: G W 4.4.0-rc4-koelsch #2123 Hardware name: Generic R8A7791 (Flattened Device Tree) [<c0017390>] (unwind_backtrace) from [<c0013094>] (show_stack+0x10/0x14) [<c0013094>] (show_stack) from [<c01ee718>] (dump_stack+0x70/0x8c) [<c01ee718>] (dump_stack) from [<c0052810>] (select_task_rq_fair+0x184/0x820) [<c0052810>] (select_task_rq_fair) from [<c004ba54>] (try_to_wake_up+0x1d0/0x340) [<c004ba54>] (try_to_wake_up) from [<c0060070>] (__wake_up_common+0x4c/0x78) [<c0060070>] (__wake_up_common) from [<c00600ac>] (__wake_up_locked+0x10/0x18) [<c00600ac>] (__wake_up_locked) from [<c006079c>] (complete+0x34/0x44) [<c006079c>] (complete) from [<c00159f8>] (arch_cpu_idle_dead+0x2c/0x8c) [<c00159f8>] (arch_cpu_idle_dead) from [<c0060a24>] (cpu_startup_entry+0x84/0x228) [<c0060a24>] (cpu_startup_entry) from [<4000a4ac>] (0x4000a4ac) CPU1: shutdown But I understand from the various other threads about this issue that this patch is not going upstream, as it papers over the real issue? Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds ^ permalink raw reply [flat|nested] 7+ messages in thread
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[not found] ` <1431467407-1223-1-git-send-email-paulmck@linux.vnet.ibm.com>
2015-05-12 21:50 ` [PATCH tip/core/rcu 7/9] arm64: Use common outgoing-CPU-notification code Paul E. McKenney
2015-05-21 8:58 ` Will Deacon
2015-05-21 12:48 ` Paul E. McKenney
2015-05-21 13:25 ` Catalin Marinas
2015-05-22 3:26 ` Paul E. McKenney
2015-05-12 21:50 ` [PATCH tip/core/rcu 8/9] arm: " Paul E. McKenney
2015-12-14 12:18 ` Geert Uytterhoeven
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