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| author |   Sven Schnelle <svens@linux.ibm.com> | 2019-12-09 09:03:12 +0100 |
|---|---|---|
| committer |   Vasily Gorbik <gor@linux.ibm.com> | 2019-12-18 23:29:26 +0100 |
| commit | 6feeee8efc53035c3195b02068b58ae947538aa4 (patch) | |
| tree | 7d7e00a80b7725e5664d44809f83b5674723528d /arch | |
| parent | Linux 5.5-rc2 (diff) | |
| download | linux-dev-6feeee8efc53035c3195b02068b58ae947538aa4.tar.xz linux-dev-6feeee8efc53035c3195b02068b58ae947538aa4.zip | |
s390/ftrace: fix endless recursion in function_graph tracer
The following sequence triggers a kernel stack overflow on s390x:
mount -t tracefs tracefs /sys/kernel/tracing
cd /sys/kernel/tracing
echo function_graph > current_tracer
[crash]
This is because preempt_count_{add,sub} are in the list of traced
functions, which can be demonstrated by:
echo preempt_count_add >set_ftrace_filter
echo function_graph > current_tracer
[crash]
The stack overflow happens because get_tod_clock_monotonic() gets called
by ftrace but itself calls preempt_{disable,enable}(), which leads to a
endless recursion. Fix this by using preempt_{disable,enable}_notrace().
Fixes: 011620688a71 ("s390/time: ensure get_clock_monotonic() returns monotonic values")
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Reviewed-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/s390/include/asm/timex.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/s390/include/asm/timex.h b/arch/s390/include/asm/timex.h index 6da8885251d6..670f14a228e5 100644 --- a/arch/s390/include/asm/timex.h +++ b/arch/s390/include/asm/timex.h @@ -194,9 +194,9 @@ static inline unsigned long long get_tod_clock_monotonic(void) { unsigned long long tod; - preempt_disable(); + preempt_disable_notrace(); tod = get_tod_clock() - *(unsigned long long *) &tod_clock_base[1]; - preempt_enable(); + preempt_enable_notrace(); return tod; } |