linux/arch/x86/power
Steven Rostedt (Red Hat) b8f99b3e0e 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>
2014-07-17 09:45:05 -04:00
..
Makefile x86: Fix resume from suspend when CONFIG_CC_STACKPROTECTOR 2009-07-08 13:20:13 +02:00
cpu.c x86, power, suspend: Annotate restore_processor_state() with notrace 2014-07-17 09:45:05 -04:00
hibernate_32.c x86-32, mm: Remove reference to resume_map_numa_kva() 2013-01-31 14:12:30 -08:00
hibernate_64.c asmlinkage, x86: Add explicit __visible to arch/x86/* 2014-05-05 16:07:44 -07:00
hibernate_asm_32.S x86, gdt, hibernate: Store/load GDT for hibernate path. 2013-05-02 11:27:35 -07:00
hibernate_asm_64.S x86, gdt, hibernate: Store/load GDT for hibernate path. 2013-05-02 11:27:35 -07:00