path: root/arch/arm64/include/asm/arch_timer.h
diff options
authorDing Tianhong <dingtianhong@huawei.com>2017-08-10 10:52:45 +0800
committerDaniel Lezcano <daniel.lezcano@linaro.org>2017-08-11 16:01:43 +0200
commitadb4f11e0a8f4e29900adb2b7af28b6bbd5c1fa4 (patch)
tree4c94934dec69bf5c73623de49c60a67f9287a289 /arch/arm64/include/asm/arch_timer.h
parentclocksource/drivers/Kconfig: Fix CLKSRC_PISTACHIO dependencies (diff)
clocksource/drivers/arm_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. 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> Acked-by: Mark Rutland <mark.rutland@arm.com> Acked-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Diffstat (limited to '')
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/arm64/include/asm/arch_timer.h b/arch/arm64/include/asm/arch_timer.h
index 74d08e44a651..a652ce0a5cb2 100644
--- a/arch/arm64/include/asm/arch_timer.h
+++ b/arch/arm64/include/asm/arch_timer.h
@@ -65,13 +65,13 @@ DECLARE_PER_CPU(const 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); \
} \