* [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
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