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linux/arch/s390/include
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Sven Schnelle 6feeee8efc 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: 011620688a ("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>
History 2019-12-18 23:29:26 +01:00
..
asm s390/ftrace: fix endless recursion in function_graph tracer 2019-12-18 23:29:26 +01:00
uapi/asm arch: ipcbuf.h: make uapi asm/ipcbuf.h self-contained 2019-12-04 19:44:14 -08:00