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author | Len Brown <len.brown@intel.com> | 2014-01-15 00:37:34 -0500 |
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committer | Ingo Molnar <mingo@kernel.org> | 2015-03-16 11:14:21 +0100 |
commit | b253149b843f89cd300cbdbea27ce1f847506f99 (patch) | |
tree | ad121a964474d5097e5d58df062d0a4215fc185d /arch/x86/include/asm/mwait.h | |
parent | 44fb085bfa17628c6d2aaa6af6b292a8499e9cbd (diff) | |
download | linux-stable-b253149b843f89cd300cbdbea27ce1f847506f99.tar.gz linux-stable-b253149b843f89cd300cbdbea27ce1f847506f99.tar.bz2 linux-stable-b253149b843f89cd300cbdbea27ce1f847506f99.zip |
sched/idle/x86: Restore mwait_idle() to fix boot hangs, to improve power savings and to improve performance
In Linux-3.9 we removed the mwait_idle() loop:
69fb3676df33 ("x86 idle: remove mwait_idle() and "idle=mwait" cmdline param")
The reasoning was that modern machines should be sufficiently
happy during the boot process using the default_idle() HALT
loop, until cpuidle loads and either acpi_idle or intel_idle
invoke the newer MWAIT-with-hints idle loop.
But two machines reported problems:
1. Certain Core2-era machines support MWAIT-C1 and HALT only.
MWAIT-C1 is preferred for optimal power and performance.
But if they support just C1, cpuidle never loads and
so they use the boot-time default idle loop forever.
2. Some laptops will boot-hang if HALT is used,
but will boot successfully if MWAIT is used.
This appears to be a hidden assumption in BIOS SMI,
that is presumably valid on the proprietary OS
where the BIOS was validated.
https://bugzilla.kernel.org/show_bug.cgi?id=60770
So here we effectively revert the patch above, restoring
the mwait_idle() loop. However, we don't bother restoring
the idle=mwait cmdline parameter, since it appears to add
no value.
Maintainer notes:
For 3.9, simply revert 69fb3676df
for 3.10, patch -F3 applies, fuzz needed due to __cpuinit use in
context For 3.11, 3.12, 3.13, this patch applies cleanly
Tested-by: Mike Galbraith <bitbucket@online.de>
Signed-off-by: Len Brown <len.brown@intel.com>
Acked-by: Mike Galbraith <bitbucket@online.de>
Cc: <stable@vger.kernel.org> # 3.9+
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ian Malone <ibmalone@gmail.com>
Cc: Josh Boyer <jwboyer@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/345254a551eb5a6a866e048d7ab570fd2193aca4.1389763084.git.len.brown@intel.com
[ Ported to recent kernels. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/include/asm/mwait.h')
-rw-r--r-- | arch/x86/include/asm/mwait.h | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/arch/x86/include/asm/mwait.h b/arch/x86/include/asm/mwait.h index a1410db38a1a..653dfa7662e1 100644 --- a/arch/x86/include/asm/mwait.h +++ b/arch/x86/include/asm/mwait.h @@ -30,6 +30,14 @@ static inline void __mwait(unsigned long eax, unsigned long ecx) :: "a" (eax), "c" (ecx)); } +static inline void __sti_mwait(unsigned long eax, unsigned long ecx) +{ + trace_hardirqs_on(); + /* "mwait %eax, %ecx;" */ + asm volatile("sti; .byte 0x0f, 0x01, 0xc9;" + :: "a" (eax), "c" (ecx)); +} + /* * This uses new MONITOR/MWAIT instructions on P4 processors with PNI, * which can obviate IPI to trigger checking of need_resched. |