MIPS: Extract schedule_mfi info from __schedule
authorTony Wu <tung7970@gmail.com>
Sun, 12 May 2013 15:05:34 +0000 (15:05 +0000)
committerRalf Baechle <ralf@linux-mips.org>
Fri, 17 May 2013 18:59:35 +0000 (20:59 +0200)
commit5000653e923de49aa282fd7d172eb6528c3ec5c7
tree8281f7a92a93c4b44af76b47c159c136905130e6
parente7438c4b893e87311d2fb0facb3e6a0df17abe01
MIPS: Extract schedule_mfi info from __schedule

schedule_mfi is supposed to be extracted from schedule(), and
is used in thread_saved_pc and get_wchan.

But, after optimization, schedule() is reduced to a sibling
call to __schedule(), and no real frame info can be extracted.

One solution is to compile schedule() with -fno-omit-frame-pointer
and -fno-optimize-sibling-calls, but that will incur performance
degradation.

Another solution is to extract info from the real scheduler,
__schedule, and this is the approache adopted here.

This patch reads the __schedule address by either following
the 'j' call in schedule if KALLSYMS is disabled or by using
kallsyms_lookup_name to lookup __schedule if KALLSYMS is
available, then, extracts schedule_mfi from __schedule frame info.

This patch also fixes the "Can't analyze schedule() prologue"
warning at boot time.

Signed-off-by: Tony Wu <tung7970@gmail.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/5237/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
arch/mips/kernel/process.c