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Date: Sun, 9 Nov 2008 21:02:33 +0100 From: Ingo Molnar <mingo@...e.hu> To: Linus Torvalds <torvalds@...ux-foundation.org> Cc: linux-kernel@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Mike Galbraith <efault@....de> Subject: Re: [git pull] scheduler warning fix * Linus Torvalds <torvalds@...ux-foundation.org> wrote: > > > On Sun, 9 Nov 2008, Ingo Molnar wrote: > > > > Please pull the latest sched-fixes-for-linus git tree from: > > > > git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip.git sched-fixes-for-linus > > > > Fixes a silly build warning that slipped through yesterday, sorry > > about that. > > Whaa? > > In file included from /home/torvalds/v2.6/linux/arch/x86/include/asm/timex.h:6, > from include/linux/timex.h:202, > from include/linux/jiffies.h:8, > from include/linux/ktime.h:25, > from include/linux/timer.h:5, > from include/linux/workqueue.h:8, > from include/linux/slub_def.h:11, > from include/linux/slab.h:124, > from include/linux/percpu.h:5, > from include/linux/rcupdate.h:39, > from include/linux/tracepoint.h:18, > from include/linux/module.h:19, > from include/linux/crypto.h:21, > from arch/x86/kernel/asm-offsets_64.c:7, > from arch/x86/kernel/asm-offsets.c:4: > /home/torvalds/v2.6/linux/arch/x86/include/asm/tsc.h: In function ‘vget_cycles’: > /home/torvalds/v2.6/linux/arch/x86/include/asm/tsc.h:46: error: ‘cycles’ undeclared (first use in this function) > /home/torvalds/v2.6/linux/arch/x86/include/asm/tsc.h:46: error: (Each undeclared identifier is reported only once > /home/torvalds/v2.6/linux/arch/x86/include/asm/tsc.h:46: error: for each function it appears in.) > make[1]: *** [arch/x86/kernel/asm-offsets.s] Error 1 > make: *** [prepare0] Error 2 > > That makes no sense. You've apparently done some idiotic rebasing of > a patch that needs to be applied on top of an earlier patch into a > tree that does _not_ need it, and then send it as a pull request. > > What _are_ you doing? Sigh, sorry - please disregard the pull request. What happened is that the cleanup patch below introduced that warning - and this morning i noticed that warning and i thought i introduced an ugly warning upstream and did a quick fix in that branch - but it didnt actually need any fixing (and in fact it broke the build). So upstream is fine and doesnt need any fix. Ingo ------------------------> >From cb9e35dce94a1b9c59d46224e8a94377d673e204 Mon Sep 17 00:00:00 2001 From: Ingo Molnar <mingo@...e.hu> Date: Sat, 8 Nov 2008 20:27:00 +0100 Subject: [PATCH] x86: clean up rdtsc_barrier() use Impact: cleanup Move rdtsc_barrier() use to vsyscall_64.c where it's relied on, and point out its role in the context of its use. Signed-off-by: Ingo Molnar <mingo@...e.hu> --- arch/x86/include/asm/tsc.h | 6 +----- arch/x86/kernel/vsyscall_64.c | 9 +++++++++ 2 files changed, 10 insertions(+), 5 deletions(-) diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h index 9cd83a8..700aeb8 100644 --- a/arch/x86/include/asm/tsc.h +++ b/arch/x86/include/asm/tsc.h @@ -44,11 +44,7 @@ static __always_inline cycles_t vget_cycles(void) if (!cpu_has_tsc) return 0; #endif - rdtsc_barrier(); - cycles = (cycles_t)__native_read_tsc(); - rdtsc_barrier(); - - return cycles; + return (cycles_t)__native_read_tsc(); } extern void tsc_init(void); diff --git a/arch/x86/kernel/vsyscall_64.c b/arch/x86/kernel/vsyscall_64.c index 0b8b669..ebf2f12 100644 --- a/arch/x86/kernel/vsyscall_64.c +++ b/arch/x86/kernel/vsyscall_64.c @@ -128,7 +128,16 @@ static __always_inline void do_vgettimeofday(struct timeval * tv) gettimeofday(tv,NULL); return; } + + /* + * Surround the RDTSC by barriers, to make sure it's not + * speculated to outside the seqlock critical section and + * does not cause time warps: + */ + rdtsc_barrier(); now = vread(); + rdtsc_barrier(); + base = __vsyscall_gtod_data.clock.cycle_last; mask = __vsyscall_gtod_data.clock.mask; mult = __vsyscall_gtod_data.clock.mult; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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