| Message ID | 1461230674-7412-1-git-send-email-lorenzo.pieralisi@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, Apr 21, 2016 at 10:24:34AM +0100, Lorenzo Pieralisi wrote: > Commit da4e4f18afe0 ("drivers/perf: arm_pmu: implement CPU_PM notifier") > added code in the arm perf infrastructure that allows the kernel to > save/restore perf counters whenever the CPU enters a low-power > state. The kernel saves/restores the counters for each active event > through the armpmu_{stop/start} ARM pmu API, so that the low-power state > enter/exit cycle is emulated through pmu start/stop operations for each > event in use. > > However, calling armpmu_start() for each active event on power up > executes code that requires RCU locking (perf_event_update_userpage()) > to be functional, so, given that the core may call the CPU_PM notifiers > while running the idle thread in an quiescent RCU state this is not > allowed as detected through the following splat when kernel is run with > CONFIG_PROVE_LOCKING enabled: > > [ 49.293286] > [ 49.294761] =============================== > [ 49.298895] [ INFO: suspicious RCU usage. ] > [ 49.303031] 4.6.0-rc3+ #421 Not tainted > [ 49.306821] ------------------------------- > [ 49.310956] include/linux/rcupdate.h:872 rcu_read_lock() used > illegally while idle! > [ 49.318530] > [ 49.318530] other info that might help us debug this: > [ 49.318530] > [ 49.326451] > [ 49.326451] RCU used illegally from idle CPU! > [ 49.326451] rcu_scheduler_active = 1, debug_locks = 0 > [ 49.337209] RCU used illegally from extended quiescent state! > [ 49.342892] 2 locks held by swapper/2/0: > [ 49.346768] #0: (cpu_pm_notifier_lock){......}, at: > [<ffffff8008163c28>] cpu_pm_exit+0x18/0x80 > [ 49.355492] #1: (rcu_read_lock){......}, at: [<ffffff800816dc38>] > perf_event_update_userpage+0x0/0x260 > > This patch wraps the armpmu_start() call (that indirectly calls > perf_event_update_userpage()) on CPU_PM notifier power state exit (or > failed entry) within the RCU_NONIDLE() macro so that the RCU subsystem > is made aware the calling cpu is not idle from an RCU perspective for > the armpmu_start() call duration, therefore fixing the issue. > > Fixes: da4e4f18afe0 ("drivers/perf: arm_pmu: implement CPU_PM notifier") > Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> > Reported-by: James Morse <james.morse@arm.com> > Suggested-by: Kevin Hilman <khilman@baylibre.com> > Cc: Ashwin Chaugule <ashwin.chaugule@linaro.org> > Cc: Will Deacon <will.deacon@arm.com> > Cc: Kevin Hilman <khilman@baylibre.com> > Cc: Sudeep Holla <sudeep.holla@arm.com> > Cc: Daniel Lezcano <daniel.lezcano@linaro.org> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> > Cc: Mathieu Poirier <mathieu.poirier@linaro.org> > Cc: Mark Rutland <mark.rutland@arm.com> FWIW: Acked-by: Mark Rutland <mark.rutland@arm.com> Thanks for fighting with this! Mark. > --- > v1 -> v2 > > - Wrapped armpmu_start() code in CPU_PM notifier within RCU_NONIDLE > - Dropped armpmu_event_set_period() refactoring > - Updated patch subject, added required tags > > v1: http://lists.infradead.org/pipermail/linux-arm-kernel/2016-April/423404.html > > drivers/perf/arm_pmu.c | 15 +++++++++++++-- > 1 file changed, 13 insertions(+), 2 deletions(-) > > diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c > index 32346b5..f700908 100644 > --- a/drivers/perf/arm_pmu.c > +++ b/drivers/perf/arm_pmu.c > @@ -737,8 +737,19 @@ static void cpu_pm_pmu_setup(struct arm_pmu *armpmu, unsigned long cmd) > break; > case CPU_PM_EXIT: > case CPU_PM_ENTER_FAILED: > - /* Restore and enable the counter */ > - armpmu_start(event, PERF_EF_RELOAD); > + /* > + * Restore and enable the counter. > + * armpmu_start() indirectly calls > + * > + * perf_event_update_userpage() > + * > + * that requires RCU read locking to be functional, > + * wrap the call within RCU_NONIDLE to make the > + * RCU subsystem aware this cpu is not idle from > + * an RCU perspective for the armpmu_start() call > + * duration. > + */ > + RCU_NONIDLE(armpmu_start(event, PERF_EF_RELOAD)); > break; > default: > break; > -- > 2.6.4 >
On Thu, Apr 21, 2016 at 10:24:34AM +0100, Lorenzo Pieralisi wrote: > Commit da4e4f18afe0 ("drivers/perf: arm_pmu: implement CPU_PM notifier") > added code in the arm perf infrastructure that allows the kernel to > save/restore perf counters whenever the CPU enters a low-power > state. The kernel saves/restores the counters for each active event > through the armpmu_{stop/start} ARM pmu API, so that the low-power state > enter/exit cycle is emulated through pmu start/stop operations for each > event in use. > > However, calling armpmu_start() for each active event on power up > executes code that requires RCU locking (perf_event_update_userpage()) > to be functional, so, given that the core may call the CPU_PM notifiers > while running the idle thread in an quiescent RCU state this is not > allowed as detected through the following splat when kernel is run with > CONFIG_PROVE_LOCKING enabled: > > [ 49.293286] > [ 49.294761] =============================== > [ 49.298895] [ INFO: suspicious RCU usage. ] > [ 49.303031] 4.6.0-rc3+ #421 Not tainted > [ 49.306821] ------------------------------- > [ 49.310956] include/linux/rcupdate.h:872 rcu_read_lock() used > illegally while idle! > [ 49.318530] > [ 49.318530] other info that might help us debug this: > [ 49.318530] > [ 49.326451] > [ 49.326451] RCU used illegally from idle CPU! > [ 49.326451] rcu_scheduler_active = 1, debug_locks = 0 > [ 49.337209] RCU used illegally from extended quiescent state! > [ 49.342892] 2 locks held by swapper/2/0: > [ 49.346768] #0: (cpu_pm_notifier_lock){......}, at: > [<ffffff8008163c28>] cpu_pm_exit+0x18/0x80 > [ 49.355492] #1: (rcu_read_lock){......}, at: [<ffffff800816dc38>] > perf_event_update_userpage+0x0/0x260 > > This patch wraps the armpmu_start() call (that indirectly calls > perf_event_update_userpage()) on CPU_PM notifier power state exit (or > failed entry) within the RCU_NONIDLE() macro so that the RCU subsystem > is made aware the calling cpu is not idle from an RCU perspective for > the armpmu_start() call duration, therefore fixing the issue. > > Fixes: da4e4f18afe0 ("drivers/perf: arm_pmu: implement CPU_PM notifier") > Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> > Reported-by: James Morse <james.morse@arm.com> > Suggested-by: Kevin Hilman <khilman@baylibre.com> > Cc: Ashwin Chaugule <ashwin.chaugule@linaro.org> > Cc: Will Deacon <will.deacon@arm.com> > Cc: Kevin Hilman <khilman@baylibre.com> > Cc: Sudeep Holla <sudeep.holla@arm.com> > Cc: Daniel Lezcano <daniel.lezcano@linaro.org> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> > Cc: Mathieu Poirier <mathieu.poirier@linaro.org> > Cc: Mark Rutland <mark.rutland@arm.com> Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > --- > v1 -> v2 > > - Wrapped armpmu_start() code in CPU_PM notifier within RCU_NONIDLE > - Dropped armpmu_event_set_period() refactoring > - Updated patch subject, added required tags > > v1: http://lists.infradead.org/pipermail/linux-arm-kernel/2016-April/423404.html > > drivers/perf/arm_pmu.c | 15 +++++++++++++-- > 1 file changed, 13 insertions(+), 2 deletions(-) > > diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c > index 32346b5..f700908 100644 > --- a/drivers/perf/arm_pmu.c > +++ b/drivers/perf/arm_pmu.c > @@ -737,8 +737,19 @@ static void cpu_pm_pmu_setup(struct arm_pmu *armpmu, unsigned long cmd) > break; > case CPU_PM_EXIT: > case CPU_PM_ENTER_FAILED: > - /* Restore and enable the counter */ > - armpmu_start(event, PERF_EF_RELOAD); > + /* > + * Restore and enable the counter. > + * armpmu_start() indirectly calls > + * > + * perf_event_update_userpage() > + * > + * that requires RCU read locking to be functional, > + * wrap the call within RCU_NONIDLE to make the > + * RCU subsystem aware this cpu is not idle from > + * an RCU perspective for the armpmu_start() call > + * duration. > + */ > + RCU_NONIDLE(armpmu_start(event, PERF_EF_RELOAD)); > break; > default: > break; > -- > 2.6.4 >
On Thu, Apr 21, 2016 at 10:24:34AM +0100, Lorenzo Pieralisi wrote: > Commit da4e4f18afe0 ("drivers/perf: arm_pmu: implement CPU_PM notifier") > added code in the arm perf infrastructure that allows the kernel to > save/restore perf counters whenever the CPU enters a low-power > state. The kernel saves/restores the counters for each active event > through the armpmu_{stop/start} ARM pmu API, so that the low-power state > enter/exit cycle is emulated through pmu start/stop operations for each > event in use. > > However, calling armpmu_start() for each active event on power up > executes code that requires RCU locking (perf_event_update_userpage()) > to be functional, so, given that the core may call the CPU_PM notifiers > while running the idle thread in an quiescent RCU state this is not > allowed as detected through the following splat when kernel is run with > CONFIG_PROVE_LOCKING enabled: > > [ 49.293286] > [ 49.294761] =============================== > [ 49.298895] [ INFO: suspicious RCU usage. ] > [ 49.303031] 4.6.0-rc3+ #421 Not tainted > [ 49.306821] ------------------------------- > [ 49.310956] include/linux/rcupdate.h:872 rcu_read_lock() used > illegally while idle! > [ 49.318530] > [ 49.318530] other info that might help us debug this: > [ 49.318530] > [ 49.326451] > [ 49.326451] RCU used illegally from idle CPU! > [ 49.326451] rcu_scheduler_active = 1, debug_locks = 0 > [ 49.337209] RCU used illegally from extended quiescent state! > [ 49.342892] 2 locks held by swapper/2/0: > [ 49.346768] #0: (cpu_pm_notifier_lock){......}, at: > [<ffffff8008163c28>] cpu_pm_exit+0x18/0x80 > [ 49.355492] #1: (rcu_read_lock){......}, at: [<ffffff800816dc38>] > perf_event_update_userpage+0x0/0x260 > > This patch wraps the armpmu_start() call (that indirectly calls > perf_event_update_userpage()) on CPU_PM notifier power state exit (or > failed entry) within the RCU_NONIDLE() macro so that the RCU subsystem > is made aware the calling cpu is not idle from an RCU perspective for > the armpmu_start() call duration, therefore fixing the issue. > > Fixes: da4e4f18afe0 ("drivers/perf: arm_pmu: implement CPU_PM notifier") > Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> > Reported-by: James Morse <james.morse@arm.com> > Suggested-by: Kevin Hilman <khilman@baylibre.com> > Cc: Ashwin Chaugule <ashwin.chaugule@linaro.org> > Cc: Will Deacon <will.deacon@arm.com> > Cc: Kevin Hilman <khilman@baylibre.com> > Cc: Sudeep Holla <sudeep.holla@arm.com> > Cc: Daniel Lezcano <daniel.lezcano@linaro.org> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> > Cc: Mathieu Poirier <mathieu.poirier@linaro.org> > Cc: Mark Rutland <mark.rutland@arm.com> Applied. Thanks.
diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c index 32346b5..f700908 100644 --- a/drivers/perf/arm_pmu.c +++ b/drivers/perf/arm_pmu.c @@ -737,8 +737,19 @@ static void cpu_pm_pmu_setup(struct arm_pmu *armpmu, unsigned long cmd) break; case CPU_PM_EXIT: case CPU_PM_ENTER_FAILED: - /* Restore and enable the counter */ - armpmu_start(event, PERF_EF_RELOAD); + /* + * Restore and enable the counter. + * armpmu_start() indirectly calls + * + * perf_event_update_userpage() + * + * that requires RCU read locking to be functional, + * wrap the call within RCU_NONIDLE to make the + * RCU subsystem aware this cpu is not idle from + * an RCU perspective for the armpmu_start() call + * duration. + */ + RCU_NONIDLE(armpmu_start(event, PERF_EF_RELOAD)); break; default: break;
Commit da4e4f18afe0 ("drivers/perf: arm_pmu: implement CPU_PM notifier") added code in the arm perf infrastructure that allows the kernel to save/restore perf counters whenever the CPU enters a low-power state. The kernel saves/restores the counters for each active event through the armpmu_{stop/start} ARM pmu API, so that the low-power state enter/exit cycle is emulated through pmu start/stop operations for each event in use. However, calling armpmu_start() for each active event on power up executes code that requires RCU locking (perf_event_update_userpage()) to be functional, so, given that the core may call the CPU_PM notifiers while running the idle thread in an quiescent RCU state this is not allowed as detected through the following splat when kernel is run with CONFIG_PROVE_LOCKING enabled: [ 49.293286] [ 49.294761] =============================== [ 49.298895] [ INFO: suspicious RCU usage. ] [ 49.303031] 4.6.0-rc3+ #421 Not tainted [ 49.306821] ------------------------------- [ 49.310956] include/linux/rcupdate.h:872 rcu_read_lock() used illegally while idle! [ 49.318530] [ 49.318530] other info that might help us debug this: [ 49.318530] [ 49.326451] [ 49.326451] RCU used illegally from idle CPU! [ 49.326451] rcu_scheduler_active = 1, debug_locks = 0 [ 49.337209] RCU used illegally from extended quiescent state! [ 49.342892] 2 locks held by swapper/2/0: [ 49.346768] #0: (cpu_pm_notifier_lock){......}, at: [<ffffff8008163c28>] cpu_pm_exit+0x18/0x80 [ 49.355492] #1: (rcu_read_lock){......}, at: [<ffffff800816dc38>] perf_event_update_userpage+0x0/0x260 This patch wraps the armpmu_start() call (that indirectly calls perf_event_update_userpage()) on CPU_PM notifier power state exit (or failed entry) within the RCU_NONIDLE() macro so that the RCU subsystem is made aware the calling cpu is not idle from an RCU perspective for the armpmu_start() call duration, therefore fixing the issue. Fixes: da4e4f18afe0 ("drivers/perf: arm_pmu: implement CPU_PM notifier") Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> Reported-by: James Morse <james.morse@arm.com> Suggested-by: Kevin Hilman <khilman@baylibre.com> Cc: Ashwin Chaugule <ashwin.chaugule@linaro.org> Cc: Will Deacon <will.deacon@arm.com> Cc: Kevin Hilman <khilman@baylibre.com> Cc: Sudeep Holla <sudeep.holla@arm.com> Cc: Daniel Lezcano <daniel.lezcano@linaro.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Mathieu Poirier <mathieu.poirier@linaro.org> Cc: Mark Rutland <mark.rutland@arm.com> --- v1 -> v2 - Wrapped armpmu_start() code in CPU_PM notifier within RCU_NONIDLE - Dropped armpmu_event_set_period() refactoring - Updated patch subject, added required tags v1: http://lists.infradead.org/pipermail/linux-arm-kernel/2016-April/423404.html drivers/perf/arm_pmu.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-)