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authorPeter Zijlstra <peterz@infradead.org>2008-07-18 18:01:23 +0200
committerIngo Molnar <mingo@elte.hu>2008-07-20 10:37:28 +0200
commit31656519e132f6612584815f128c83976a9aaaef (patch)
tree595349fdcd65988d7a43d647594dcea8a8a4e80b /kernel/Kconfig.hz
parent577b4a58d2e74a4d48050eeea3e3f952ce04eb86 (diff)
downloadlinux-sh-31656519e132f6612584815f128c83976a9aaaef.tar.gz
sched, x86: clean up hrtick implementation
random uvesafb failures were reported against Gentoo: http://bugs.gentoo.org/show_bug.cgi?id=222799 and Mihai Moldovan bisected it back to: > 8f4d37ec073c17e2d4aa8851df5837d798606d6f is first bad commit > commit 8f4d37ec073c17e2d4aa8851df5837d798606d6f > Author: Peter Zijlstra <a.p.zijlstra@chello.nl> > Date: Fri Jan 25 21:08:29 2008 +0100 > > sched: high-res preemption tick Linus suspected it to be hrtick + vm86 interaction and observed: > Btw, Peter, Ingo: I think that commit is doing bad things. They aren't > _incorrect_ per se, but they are definitely bad. > > Why? > > Using random _TIF_WORK_MASK flags is really impolite for doing > "scheduling" work. There's a reason that arch/x86/kernel/entry_32.S > special-cases the _TIF_NEED_RESCHED flag: we don't want to exit out of > vm86 mode unnecessarily. > > See the "work_notifysig_v86" label, and how it does that > "save_v86_state()" thing etc etc. Right, I never liked having to fiddle with those TIF flags. Initially I needed it because the hrtimer base lock could not nest in the rq lock. That however is fixed these days. Currently the only reason left to fiddle with the TIF flags is remote wakeups. We cannot program a remote cpu's hrtimer. I've been thinking about using the new and improved IPI function call stuff to implement hrtimer_start_on(). However that does require that smp_call_function_single(.wait=0) works from interrupt context - /me looks at the latest series from Jens - Yes that does seem to be supported, good. Here's a stab at cleaning this stuff up ... Mihai reported test success as well. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Tested-by: Mihai Moldovan <ionic@ionic.de> Cc: Michal Januszewski <spock@gentoo.org> Cc: Antonino Daplas <adaplas@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/Kconfig.hz')
-rw-r--r--kernel/Kconfig.hz2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/Kconfig.hz b/kernel/Kconfig.hz
index 526128a2e622..2a202a846757 100644
--- a/kernel/Kconfig.hz
+++ b/kernel/Kconfig.hz
@@ -55,4 +55,4 @@ config HZ
default 1000 if HZ_1000
config SCHED_HRTICK
- def_bool HIGH_RES_TIMERS && X86
+ def_bool HIGH_RES_TIMERS