* [PATCH v2] drivers/perf: arm-pmu: fix RCU usage on pmu resume from low-power
@ 2016-04-21 9:24 Lorenzo Pieralisi
2016-04-21 10:12 ` Mark Rutland
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: Lorenzo Pieralisi @ 2016-04-21 9:24 UTC (permalink / raw)
To: linux-arm-kernel
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(-)
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
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH v2] drivers/perf: arm-pmu: fix RCU usage on pmu resume from low-power
2016-04-21 9:24 [PATCH v2] drivers/perf: arm-pmu: fix RCU usage on pmu resume from low-power Lorenzo Pieralisi
@ 2016-04-21 10:12 ` Mark Rutland
2016-04-21 12:50 ` Paul E. McKenney
2016-04-21 13:47 ` Catalin Marinas
2 siblings, 0 replies; 4+ messages in thread
From: Mark Rutland @ 2016-04-21 10:12 UTC (permalink / raw)
To: linux-arm-kernel
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
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH v2] drivers/perf: arm-pmu: fix RCU usage on pmu resume from low-power
2016-04-21 9:24 [PATCH v2] drivers/perf: arm-pmu: fix RCU usage on pmu resume from low-power Lorenzo Pieralisi
2016-04-21 10:12 ` Mark Rutland
@ 2016-04-21 12:50 ` Paul E. McKenney
2016-04-21 13:47 ` Catalin Marinas
2 siblings, 0 replies; 4+ messages in thread
From: Paul E. McKenney @ 2016-04-21 12:50 UTC (permalink / raw)
To: linux-arm-kernel
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
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH v2] drivers/perf: arm-pmu: fix RCU usage on pmu resume from low-power
2016-04-21 9:24 [PATCH v2] drivers/perf: arm-pmu: fix RCU usage on pmu resume from low-power Lorenzo Pieralisi
2016-04-21 10:12 ` Mark Rutland
2016-04-21 12:50 ` Paul E. McKenney
@ 2016-04-21 13:47 ` Catalin Marinas
2 siblings, 0 replies; 4+ messages in thread
From: Catalin Marinas @ 2016-04-21 13:47 UTC (permalink / raw)
To: linux-arm-kernel
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.
--
Catalin
^ permalink raw reply [flat|nested] 4+ messages in thread
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2016-04-21 9:24 [PATCH v2] drivers/perf: arm-pmu: fix RCU usage on pmu resume from low-power Lorenzo Pieralisi
2016-04-21 10:12 ` Mark Rutland
2016-04-21 12:50 ` Paul E. McKenney
2016-04-21 13:47 ` Catalin Marinas
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