bug. This bug has been there sinc function tracing was added way back
when. But my new development depends on this bug being fixed, and it
should be fixed regardless as it causes ftrace to disable itself when
triggered, and a reboot is required to enable it again.
The bug is that the function probe does not disable itself properly
if there's another probe of its type still enabled. For example:
# cd /sys/kernel/debug/tracing
# echo schedule:traceoff > set_ftrace_filter
# echo do_IRQ:traceoff > set_ftrace_filter
# echo \!do_IRQ:traceoff > /debug/tracing/set_ftrace_filter
# echo do_IRQ:traceoff > set_ftrace_filter
The above registers two traceoff probes (one for schedule and one for
do_IRQ, and then removes do_IRQ. But since there still exists one for
schedule, it is not done properly. When adding do_IRQ back, the breakage
in the accounting is noticed by the ftrace self tests, and it causes
a warning and disables ftrace.
-----BEGIN PGP SIGNATURE-----
iQExBAABCAAbBQJY8ovvFBxyb3N0ZWR0QGdvb2RtaXMub3JnAAoJEMm5BfJq2Y3L
nkAH/jfsXUWIbZ6J0A7+nmGiBdIVwLwG0ZOJClcxjnCSpsNs+FO/0w6ragtIYCi2
Km+0s/slA5GOddG4Miga/dhtxGhDosyXnxqC+4GmD0maqJGLweJLbmiQ1xhra0hr
XGDI+SXHM/n22zVkFEbkGXgxMvOHeR+X/sREZo3XmoXRLbc1QVtTEe/8TdlLXwE5
5Fs07xSQqx4TS7oBxIjipHnbHL/gIktEo0HiEmq73++r42MztIMYZPoV+cXuim37
C6xO4PxfPN0aRh9W5gdiMnbv6lummVBNQXwpMya0vTbxz/9WeUex8c+lcInQUJgA
FhQWKaCGyi0UK4Pa2Pz/Dmxuti0=
=LYLo
-----END PGP SIGNATURE-----
Merge tag 'trace-v4.11-rc5-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
Pull ftrace fix from Steven Rostedt:
"While rewriting the function probe code, I stumbled over a long
standing bug. This bug has been there sinc function tracing was added
way back when. But my new development depends on this bug being fixed,
and it should be fixed regardless as it causes ftrace to disable
itself when triggered, and a reboot is required to enable it again.
The bug is that the function probe does not disable itself properly if
there's another probe of its type still enabled. For example:
# cd /sys/kernel/debug/tracing
# echo schedule:traceoff > set_ftrace_filter
# echo do_IRQ:traceoff > set_ftrace_filter
# echo \!do_IRQ:traceoff > /debug/tracing/set_ftrace_filter
# echo do_IRQ:traceoff > set_ftrace_filter
The above registers two traceoff probes (one for schedule and one for
do_IRQ, and then removes do_IRQ.
But since there still exists one for schedule, it is not done
properly. When adding do_IRQ back, the breakage in the accounting is
noticed by the ftrace self tests, and it causes a warning and disables
ftrace"
* tag 'trace-v4.11-rc5-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
ftrace: Fix removing of second function probe
48538861b9