From: Steven Rostedt (Red Hat) Date: Wed, 25 Jun 2014 00:58:26 +0000 (-0400) Subject: x86, power, suspend: Annotate restore_processor_state() with notrace X-Git-Tag: cleanup-for-v3.18~145^2~33 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b8f99b3e0e066e7b2f3dbc348fe33d8277950727;p=pandora-kernel.git 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" Reviewed-by: Masami Hiramatsu Signed-off-by: Steven Rostedt --- Reading git-diff-tree failed