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* linux/seqlock.h should #include asm/processor.h for cpu_relax()David Howells2011-06-111-0/+1
| | | | | | | | | | | | | | | | | | | It uses cpu_relax(), and so needs <asm/processor.h> Without this patch, I see: CC arch/mn10300/kernel/asm-offsets.s In file included from include/linux/time.h:8, from include/linux/timex.h:56, from include/linux/sched.h:57, from arch/mn10300/kernel/asm-offsets.c:7: include/linux/seqlock.h: In function 'read_seqbegin': include/linux/seqlock.h:91: error: implicit declaration of function 'cpu_relax' whilst building asb2364_defconfig on MN10300. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* seqlock: Get rid of SEQLOCK_UNLOCKEDEric Dumazet2011-05-241-3/+0
| | | | | | | | | | | | All static seqlock should be initialized with the lockdep friendly __SEQLOCK_UNLOCKED() macro. Remove legacy SEQLOCK_UNLOCKED() macro. Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Cc: David Miller <davem@davemloft.net> Link: http://lkml.kernel.org/r/%3C1306238888.3026.31.camel%40edumazet-laptop%3E Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
* seqlock: Don't smp_rmb in seqlock reader spin loopMilton Miller2011-05-121-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Move the smp_rmb after cpu_relax loop in read_seqlock and add ACCESS_ONCE to make sure the test and return are consistent. A multi-threaded core in the lab didn't like the update from 2.6.35 to 2.6.36, to the point it would hang during boot when multiple threads were active. Bisection showed af5ab277ded04bd9bc6b048c5a2f0e7d70ef0867 (clockevents: Remove the per cpu tick skew) as the culprit and it is supported with stack traces showing xtime_lock waits including tick_do_update_jiffies64 and/or update_vsyscall. Experimentation showed the combination of cpu_relax and smp_rmb was significantly slowing the progress of other threads sharing the core, and this patch is effective in avoiding the hang. A theory is the rmb is affecting the whole core while the cpu_relax is causing a resource rebalance flush, together they cause an interfernce cadance that is unbroken when the seqlock reader has interrupts disabled. At first I was confused why the refactor in 3c22cd5709e8143444a6d08682a87f4c57902df3 (kernel: optimise seqlock) didn't affect this patch application, but after some study that affected seqcount not seqlock. The new seqcount was not factored back into the seqlock. I defer that the future. While the removal of the timer interrupt offset created contention for the xtime lock while a cpu does the additonal work to update the system clock, the seqlock implementation with the tight rmb spin loop goes back much further, and is just waiting for the right trigger. Cc: <stable@vger.kernel.org> Signed-off-by: Milton Miller <miltonm@bga.com> Cc: <linuxppc-dev@lists.ozlabs.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andi Kleen <andi@firstfloor.org> Cc: Nick Piggin <npiggin@kernel.dk> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Anton Blanchard <anton@samba.org> Cc: Paul McKenney <paulmck@linux.vnet.ibm.com> Acked-by: Eric Dumazet <eric.dumazet@gmail.com> Link: http://lkml.kernel.org/r/%3Cseqlock-rmb%40mdm.bga.com%3E Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
* kernel: optimise seqlockNick Piggin2011-01-071-7/+73
| | | | | | | | | Add branch annotations for seqlock read fastpath, and introduce __read_seqcount_begin and __read_seqcount_end functions, that can avoid the smp_rmb() if used carefully. These will be used by store-free path walking algorithm performance is critical and seqlocks are in use. Signed-off-by: Nick Piggin <npiggin@kernel.dk>
* seqlock: livelock fixIngo Molnar2008-04-251-17/+29
| | | | | | | | Thomas Gleixner debugged a particularly ugly seqlock related livelock: do not process the seq-read section if we know it beforehand that the test at the end of the section will fail ... Signed-off-by: Ingo Molnar <mingo@elte.hu>
* seqlocks: trivial remove weird whitespaceDaniel Walker2007-04-271-4/+4
| | | | | Signed-off-by: Daniel Walker <dwalker@mvista.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* Various typo fixes.Robert P. J. Day2007-02-171-1/+1
| | | | | | | | Correct mis-spellings of "algorithm", "appear", "consistent" and (shame, shame) "kernel". Signed-off-by: Robert P. J. Day <rpjday@mindspring.com> Signed-off-by: Adrian Bunk <bunk@stusta.de>
* [PATCH] lockdep: fix seqlock_init()Ingo Molnar2006-12-121-2/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | seqlock_init() needs to use spin_lock_init() for dynamic locks, so that lockdep is notified about the presence of a new lock. (this is a fallout of the recent networking merge, which started using the so-far unused seqlock_init() API.) This fix solves the following lockdep-internal warning on current -git: INFO: trying to register non-static key. the code is fine but needs lockdep annotation. turning off the locking correctness validator. __lock_acquire+0x10c/0x9f9 lock_acquire+0x56/0x72 _spin_lock+0x35/0x42 neigh_destroy+0x9d/0x12e neigh_periodic_timer+0x10a/0x15c run_timer_softirq+0x126/0x18e __do_softirq+0x6b/0xe6 do_softirq+0x64/0xd2 ksoftirqd+0x82/0x138 Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] lockdep: locking init debugging improvementIngo Molnar2006-07-031-2/+10
| | | | | | | | | | | | Locking init improvement: - introduce and use __SPIN_LOCK_UNLOCKED for array initializations, to pass in the name string of locks, used by debugging Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Arjan van de Ven <arjan@linux.intel.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* Don't include linux/config.h from anywhere else in include/David Woodhouse2006-04-261-1/+0
| | | | Signed-off-by: David Woodhouse <dwmw2@infradead.org>
* [PATCH] x86_64: inline function prefix with __always_inline in vsyscallmao, bibo2006-04-111-2/+2
| | | | | | | | | | | | In vsyscall function do_vgettimeofday(), some functions are declared as inlined, which is a hint for gcc to compile the function inlined but it not forced. Sometimes compiler does not compile the function as inlined, so here inline is replaced by __always_inline prefix. It does not happen in gcc compiler actually, but it possibly happens. Signed-off-by: bibo mao <bibo.mao@intel.com> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* Linux-2.6.12-rc2v2.6.12-rc2Linus Torvalds2005-04-161-0/+175
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!