* [PATCH RESEND] arm64: arch_timer: fix the infinite recursion when enable ftrace and erratum workaround
@ 2017-07-09 8:30 Ding Tianhong
2017-07-10 6:12 ` Hanjun Guo
2017-07-10 11:22 ` Mark Rutland
0 siblings, 2 replies; 6+ messages in thread
From: Ding Tianhong @ 2017-07-09 8:30 UTC (permalink / raw)
To: linux-arm-kernel
When enable preempt and debug ftrace, and perform the following steps, the
system will hang:
mount -t debugfs nodev /sys/kernel/debug/
cd /sys/kernel/debug/tracing/
echo function_graph > current_tracer
This is because tracing the preempt_disable/enable calls would cause
trace_clock() which would get local timer to go into infinite recursion
when enable the arch timer erratum workaround for some chips, so Prevent
tracing of preempt_disable/enable() in arch_timer_reg_read_stable().
This problem is similar to the fixed by upstream commit 96b3d28bf4
("sched/clock: Prevent tracing recursion in sched_clock_cpu()").
Fixes: 6acc71ccac71 ("arm64: arch_timer: Allows a CPU-specific erratum to only affect a subset of CPUs")
Signed-off-by: Ding Tianhong <dingtianhong@huawei.com>
---
arch/arm64/include/asm/arch_timer.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/include/asm/arch_timer.h b/arch/arm64/include/asm/arch_timer.h
index 74d08e4..67bb7a4 100644
--- a/arch/arm64/include/asm/arch_timer.h
+++ b/arch/arm64/include/asm/arch_timer.h
@@ -65,13 +65,13 @@ struct arch_timer_erratum_workaround {
u64 _val; \
if (needs_unstable_timer_counter_workaround()) { \
const struct arch_timer_erratum_workaround *wa; \
- preempt_disable(); \
+ preempt_disable_notrace(); \
wa = __this_cpu_read(timer_unstable_counter_workaround); \
if (wa && wa->read_##reg) \
_val = wa->read_##reg(); \
else \
_val = read_sysreg(reg); \
- preempt_enable(); \
+ preempt_enable_notrace(); \
} else { \
_val = read_sysreg(reg); \
} \
--
1.9.0
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH RESEND] arm64: arch_timer: fix the infinite recursion when enable ftrace and erratum workaround
2017-07-09 8:30 [PATCH RESEND] arm64: arch_timer: fix the infinite recursion when enable ftrace and erratum workaround Ding Tianhong
@ 2017-07-10 6:12 ` Hanjun Guo
2017-07-10 11:22 ` Mark Rutland
1 sibling, 0 replies; 6+ messages in thread
From: Hanjun Guo @ 2017-07-10 6:12 UTC (permalink / raw)
To: linux-arm-kernel
On 2017/7/9 16:30, Ding Tianhong wrote:
> When enable preempt and debug ftrace, and perform the following steps, the
> system will hang:
> mount -t debugfs nodev /sys/kernel/debug/
> cd /sys/kernel/debug/tracing/
> echo function_graph > current_tracer
>
> This is because tracing the preempt_disable/enable calls would cause
> trace_clock() which would get local timer to go into infinite recursion
> when enable the arch timer erratum workaround for some chips, so Prevent
> tracing of preempt_disable/enable() in arch_timer_reg_read_stable().
>
> This problem is similar to the fixed by upstream commit 96b3d28bf4
> ("sched/clock: Prevent tracing recursion in sched_clock_cpu()").
>
> Fixes: 6acc71ccac71 ("arm64: arch_timer: Allows a CPU-specific erratum to only affect a subset of CPUs")
> Signed-off-by: Ding Tianhong <dingtianhong@huawei.com>
> ---
> arch/arm64/include/asm/arch_timer.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/include/asm/arch_timer.h b/arch/arm64/include/asm/arch_timer.h
> index 74d08e4..67bb7a4 100644
> --- a/arch/arm64/include/asm/arch_timer.h
> +++ b/arch/arm64/include/asm/arch_timer.h
> @@ -65,13 +65,13 @@ struct arch_timer_erratum_workaround {
> u64 _val; \
> if (needs_unstable_timer_counter_workaround()) { \
> const struct arch_timer_erratum_workaround *wa; \
> - preempt_disable(); \
> + preempt_disable_notrace(); \
> wa = __this_cpu_read(timer_unstable_counter_workaround); \
> if (wa && wa->read_##reg) \
> _val = wa->read_##reg(); \
> else \
> _val = read_sysreg(reg); \
> - preempt_enable(); \
> + preempt_enable_notrace(); \
> } else { \
> _val = read_sysreg(reg); \
> } \
This fixes my system hang issue when I using function tracer with
enabled timer errata on D03,
Tested-by: Hanjun Guo <hanjun.guo@linaro.org>
Thanks
Hanjun
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH RESEND] arm64: arch_timer: fix the infinite recursion when enable ftrace and erratum workaround
2017-07-09 8:30 [PATCH RESEND] arm64: arch_timer: fix the infinite recursion when enable ftrace and erratum workaround Ding Tianhong
2017-07-10 6:12 ` Hanjun Guo
@ 2017-07-10 11:22 ` Mark Rutland
2017-07-10 13:54 ` Marc Zyngier
2017-07-26 2:42 ` Ding Tianhong
1 sibling, 2 replies; 6+ messages in thread
From: Mark Rutland @ 2017-07-10 11:22 UTC (permalink / raw)
To: linux-arm-kernel
On Sun, Jul 09, 2017 at 04:30:54PM +0800, Ding Tianhong wrote:
> When enable preempt and debug ftrace, and perform the following steps, the
> system will hang:
> mount -t debugfs nodev /sys/kernel/debug/
> cd /sys/kernel/debug/tracing/
> echo function_graph > current_tracer
>
> This is because tracing the preempt_disable/enable calls would cause
> trace_clock() which would get local timer to go into infinite recursion
> when enable the arch timer erratum workaround for some chips, so Prevent
> tracing of preempt_disable/enable() in arch_timer_reg_read_stable().
>
> This problem is similar to the fixed by upstream commit 96b3d28bf4
> ("sched/clock: Prevent tracing recursion in sched_clock_cpu()").
As I mentioned before, the patch itself looks fine to me, but the commit
message is somewhat difficult to read.
Can we please change this to:
arm64: arch_timer: avoid infinite recursion when ftrace is enabled
On platforms with an arch timer erratum workaround, it's possible for
arch_timer_reg_read_stable() to recurse into itself when certain
tracing options are enabled, leading to stack overflows and related
problems.
For example, when PREEMPT_TRACER and FUNCTION_GRAPH_TRACER are
selected, it's possible to trigger this with:
$ mount -t debugfs nodev /sys/kernel/debug/
$ echo function_graph > /sys/kernel/debug/tracing/current_tracer
The problem is that in such cases, preempt_disable() instrumentation
attempts to acquire a timestamp via trace_clock(), resulting in a call
back to arch_timer_reg_read_stable(), and hence recursion.
This patch changes arch_timer_reg_read_stable() to use
preempt_{disable,enable}_notrace(), which avoids this.
With that commit message:
Acked-by: Mark Rutland <mark.rutland@arm.com>
Daniel, Thomas, would you be happy to fold that in when picking this? Or
would you prefer that I fix this up and resend?
Thanks,
Mark.
> Fixes: 6acc71ccac71 ("arm64: arch_timer: Allows a CPU-specific erratum to only affect a subset of CPUs")
> Signed-off-by: Ding Tianhong <dingtianhong@huawei.com>
> ---
> arch/arm64/include/asm/arch_timer.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/include/asm/arch_timer.h b/arch/arm64/include/asm/arch_timer.h
> index 74d08e4..67bb7a4 100644
> --- a/arch/arm64/include/asm/arch_timer.h
> +++ b/arch/arm64/include/asm/arch_timer.h
> @@ -65,13 +65,13 @@ struct arch_timer_erratum_workaround {
> u64 _val; \
> if (needs_unstable_timer_counter_workaround()) { \
> const struct arch_timer_erratum_workaround *wa; \
> - preempt_disable(); \
> + preempt_disable_notrace(); \
> wa = __this_cpu_read(timer_unstable_counter_workaround); \
> if (wa && wa->read_##reg) \
> _val = wa->read_##reg(); \
> else \
> _val = read_sysreg(reg); \
> - preempt_enable(); \
> + preempt_enable_notrace(); \
> } else { \
> _val = read_sysreg(reg); \
> } \
> --
> 1.9.0
>
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH RESEND] arm64: arch_timer: fix the infinite recursion when enable ftrace and erratum workaround
2017-07-10 11:22 ` Mark Rutland
@ 2017-07-10 13:54 ` Marc Zyngier
2017-07-26 2:42 ` Ding Tianhong
1 sibling, 0 replies; 6+ messages in thread
From: Marc Zyngier @ 2017-07-10 13:54 UTC (permalink / raw)
To: linux-arm-kernel
On 10/07/17 12:22, Mark Rutland wrote:
> On Sun, Jul 09, 2017 at 04:30:54PM +0800, Ding Tianhong wrote:
>> When enable preempt and debug ftrace, and perform the following steps, the
>> system will hang:
>> mount -t debugfs nodev /sys/kernel/debug/
>> cd /sys/kernel/debug/tracing/
>> echo function_graph > current_tracer
>>
>> This is because tracing the preempt_disable/enable calls would cause
>> trace_clock() which would get local timer to go into infinite recursion
>> when enable the arch timer erratum workaround for some chips, so Prevent
>> tracing of preempt_disable/enable() in arch_timer_reg_read_stable().
>>
>> This problem is similar to the fixed by upstream commit 96b3d28bf4
>> ("sched/clock: Prevent tracing recursion in sched_clock_cpu()").
>
> As I mentioned before, the patch itself looks fine to me, but the commit
> message is somewhat difficult to read.
>
> Can we please change this to:
>
> arm64: arch_timer: avoid infinite recursion when ftrace is enabled
>
> On platforms with an arch timer erratum workaround, it's possible for
> arch_timer_reg_read_stable() to recurse into itself when certain
> tracing options are enabled, leading to stack overflows and related
> problems.
>
> For example, when PREEMPT_TRACER and FUNCTION_GRAPH_TRACER are
> selected, it's possible to trigger this with:
>
> $ mount -t debugfs nodev /sys/kernel/debug/
> $ echo function_graph > /sys/kernel/debug/tracing/current_tracer
>
> The problem is that in such cases, preempt_disable() instrumentation
> attempts to acquire a timestamp via trace_clock(), resulting in a call
> back to arch_timer_reg_read_stable(), and hence recursion.
>
> This patch changes arch_timer_reg_read_stable() to use
> preempt_{disable,enable}_notrace(), which avoids this.
>
> With that commit message:
>
> Acked-by: Mark Rutland <mark.rutland@arm.com>
>
> Daniel, Thomas, would you be happy to fold that in when picking this? Or
> would you prefer that I fix this up and resend?
With the proposed changes:
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
M.
--
Jazz is not dead. It just smells funny...
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH RESEND] arm64: arch_timer: fix the infinite recursion when enable ftrace and erratum workaround
2017-07-10 11:22 ` Mark Rutland
2017-07-10 13:54 ` Marc Zyngier
@ 2017-07-26 2:42 ` Ding Tianhong
2017-07-31 15:33 ` Daniel Lezcano
1 sibling, 1 reply; 6+ messages in thread
From: Ding Tianhong @ 2017-07-26 2:42 UTC (permalink / raw)
To: linux-arm-kernel
On 2017/7/10 19:22, Mark Rutland wrote:
> On Sun, Jul 09, 2017 at 04:30:54PM +0800, Ding Tianhong wrote:
>> When enable preempt and debug ftrace, and perform the following steps, the
>> system will hang:
>> mount -t debugfs nodev /sys/kernel/debug/
>> cd /sys/kernel/debug/tracing/
>> echo function_graph > current_tracer
>>
>> This is because tracing the preempt_disable/enable calls would cause
>> trace_clock() which would get local timer to go into infinite recursion
>> when enable the arch timer erratum workaround for some chips, so Prevent
>> tracing of preempt_disable/enable() in arch_timer_reg_read_stable().
>>
>> This problem is similar to the fixed by upstream commit 96b3d28bf4
>> ("sched/clock: Prevent tracing recursion in sched_clock_cpu()").
>
> As I mentioned before, the patch itself looks fine to me, but the commit
> message is somewhat difficult to read.
>
> Can we please change this to:
>
> arm64: arch_timer: avoid infinite recursion when ftrace is enabled
>
> On platforms with an arch timer erratum workaround, it's possible for
> arch_timer_reg_read_stable() to recurse into itself when certain
> tracing options are enabled, leading to stack overflows and related
> problems.
>
> For example, when PREEMPT_TRACER and FUNCTION_GRAPH_TRACER are
> selected, it's possible to trigger this with:
>
> $ mount -t debugfs nodev /sys/kernel/debug/
> $ echo function_graph > /sys/kernel/debug/tracing/current_tracer
>
> The problem is that in such cases, preempt_disable() instrumentation
> attempts to acquire a timestamp via trace_clock(), resulting in a call
> back to arch_timer_reg_read_stable(), and hence recursion.
>
> This patch changes arch_timer_reg_read_stable() to use
> preempt_{disable,enable}_notrace(), which avoids this.
>
> With that commit message:
>
> Acked-by: Mark Rutland <mark.rutland@arm.com>
>
> Daniel, Thomas, would you be happy to fold that in when picking this? Or
> would you prefer that I fix this up and resend?
>
Hi Danial, Thomas:
It looks didn't merge to the mainline tree yet, should I update the commit and
resend this patch again?
Thanks
Ding
> Thanks,
> Mark.
>
>> Fixes: 6acc71ccac71 ("arm64: arch_timer: Allows a CPU-specific erratum to only affect a subset of CPUs")
>> Signed-off-by: Ding Tianhong <dingtianhong@huawei.com>
>> ---
>> arch/arm64/include/asm/arch_timer.h | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/arch_timer.h b/arch/arm64/include/asm/arch_timer.h
>> index 74d08e4..67bb7a4 100644
>> --- a/arch/arm64/include/asm/arch_timer.h
>> +++ b/arch/arm64/include/asm/arch_timer.h
>> @@ -65,13 +65,13 @@ struct arch_timer_erratum_workaround {
>> u64 _val; \
>> if (needs_unstable_timer_counter_workaround()) { \
>> const struct arch_timer_erratum_workaround *wa; \
>> - preempt_disable(); \
>> + preempt_disable_notrace(); \
>> wa = __this_cpu_read(timer_unstable_counter_workaround); \
>> if (wa && wa->read_##reg) \
>> _val = wa->read_##reg(); \
>> else \
>> _val = read_sysreg(reg); \
>> - preempt_enable(); \
>> + preempt_enable_notrace(); \
>> } else { \
>> _val = read_sysreg(reg); \
>> } \
>> --
>> 1.9.0
>>
>>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>
> .
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH RESEND] arm64: arch_timer: fix the infinite recursion when enable ftrace and erratum workaround
2017-07-26 2:42 ` Ding Tianhong
@ 2017-07-31 15:33 ` Daniel Lezcano
0 siblings, 0 replies; 6+ messages in thread
From: Daniel Lezcano @ 2017-07-31 15:33 UTC (permalink / raw)
To: linux-arm-kernel
On 26/07/2017 04:42, Ding Tianhong wrote:
>
>
> On 2017/7/10 19:22, Mark Rutland wrote:
>> On Sun, Jul 09, 2017 at 04:30:54PM +0800, Ding Tianhong wrote:
>>> When enable preempt and debug ftrace, and perform the following steps, the
>>> system will hang:
>>> mount -t debugfs nodev /sys/kernel/debug/
>>> cd /sys/kernel/debug/tracing/
>>> echo function_graph > current_tracer
>>>
>>> This is because tracing the preempt_disable/enable calls would cause
>>> trace_clock() which would get local timer to go into infinite recursion
>>> when enable the arch timer erratum workaround for some chips, so Prevent
>>> tracing of preempt_disable/enable() in arch_timer_reg_read_stable().
>>>
>>> This problem is similar to the fixed by upstream commit 96b3d28bf4
>>> ("sched/clock: Prevent tracing recursion in sched_clock_cpu()").
>>
>> As I mentioned before, the patch itself looks fine to me, but the commit
>> message is somewhat difficult to read.
>>
>> Can we please change this to:
>>
>> arm64: arch_timer: avoid infinite recursion when ftrace is enabled
>>
>> On platforms with an arch timer erratum workaround, it's possible for
>> arch_timer_reg_read_stable() to recurse into itself when certain
>> tracing options are enabled, leading to stack overflows and related
>> problems.
>>
>> For example, when PREEMPT_TRACER and FUNCTION_GRAPH_TRACER are
>> selected, it's possible to trigger this with:
>>
>> $ mount -t debugfs nodev /sys/kernel/debug/
>> $ echo function_graph > /sys/kernel/debug/tracing/current_tracer
>>
>> The problem is that in such cases, preempt_disable() instrumentation
>> attempts to acquire a timestamp via trace_clock(), resulting in a call
>> back to arch_timer_reg_read_stable(), and hence recursion.
>>
>> This patch changes arch_timer_reg_read_stable() to use
>> preempt_{disable,enable}_notrace(), which avoids this.
>>
>> With that commit message:
>>
>> Acked-by: Mark Rutland <mark.rutland@arm.com>
>>
>> Daniel, Thomas, would you be happy to fold that in when picking this? Or
>> would you prefer that I fix this up and resend?
>>
>
> Hi Danial, Thomas:
>
> It looks didn't merge to the mainline tree yet, should I update the commit and
> resend this patch again?
>
Yes, please. I'm coming back from two weeks OoO, that will help.
Thanks.
-- Daniel
--
<http://www.linaro.org/> Linaro.org ? Open source software for ARM SoCs
Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook |
<http://twitter.com/#!/linaroorg> Twitter |
<http://www.linaro.org/linaro-blog/> Blog
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2017-07-31 15:33 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2017-07-09 8:30 [PATCH RESEND] arm64: arch_timer: fix the infinite recursion when enable ftrace and erratum workaround Ding Tianhong
2017-07-10 6:12 ` Hanjun Guo
2017-07-10 11:22 ` Mark Rutland
2017-07-10 13:54 ` Marc Zyngier
2017-07-26 2:42 ` Ding Tianhong
2017-07-31 15:33 ` Daniel Lezcano
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).