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author | Steven Rostedt (Red Hat) <rostedt@goodmis.org> | 2014-06-24 20:58:26 -0400 |
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committer | Steven Rostedt <rostedt@goodmis.org> | 2014-07-17 09:45:05 -0400 |
commit | b8f99b3e0e066e7b2f3dbc348fe33d8277950727 (patch) | |
tree | 6ab3e2db3400980c723ff5d8cf64252a7be2a2c8 /kernel/power | |
parent | 1026ff9b8e6cbb112fd708b2e62f1812ce9a4e01 (diff) | |
download | op-kernel-dev-b8f99b3e0e066e7b2f3dbc348fe33d8277950727.zip op-kernel-dev-b8f99b3e0e066e7b2f3dbc348fe33d8277950727.tar.gz |
x86, power, suspend: Annotate restore_processor_state() with notrace
ftrace_stop() is used to stop function tracing during suspend and resume
which removes a lot of possible debugging opportunities with tracing.
The reason was that some function in the resume path was causing a triple
fault if it were to be traced. The issue I found was that doing something
as simple as calling smp_processor_id() would reboot the box!
When function tracing was first created I didn't have a good way to figure
out what function was having issues, or it looked to be multiple ones. To
fix it, we just created a big hammer approach to the problem which was to
add a flag in the mcount trampoline that could be checked and not call
the traced functions.
Lately I developed better ways to find problem functions and I can bisect
down to see what function is causing the issue. I removed the flag that
stopped tracing and proceeded to find the problem function and it ended
up being restore_processor_state(). This function makes sense as when the
CPU comes back online from a suspend it calls this function to set up
registers, amongst them the GS register, which stores things such as
what CPU the processor is (if you call smp_processor_id() without this
set up properly, it would fault).
By making restore_processor_state() notrace, the system can suspend and
resume without the need of the big hammer tracing to stop.
Link: http://lkml.kernel.org/r/3577662.BSnUZfboWb@vostro.rjw.lan
Acked-by: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'kernel/power')
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