After merging the block tree, 20100414's linux-next build (x86_64 allmodconfig) failed like this: ERROR: "get_gendisk" [block/blk-cgroup.ko] undefined! ERROR: "sched_clock" [block/blk-cgroup.ko] undefined! This happens because the two symbols aren't exported and hence not available when blk-cgroup code is built as a module. I've tried to stay consistent with the use of EXPORT_SYMBOL or EXPORT_SYMBOL_GPL with the other symbols in the respective files. Signed-off-by: Divyesh Shah <dpshah@google.com> Acked-by: Gui Jianfeng <guijianfeng@cn.fujitsu.cn> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Relax stable-sched-clock architectures to not save/disable/restore hardirqs in cpu_clock(). The background is that I was trying to resolve a sparc64 perf issue when I discovered this problem. On sparc64 I implement pseudo NMIs by simply running the kernel at IRQ level 14 when local_irq_disable() is called, this allows performance counter events to still come in at IRQ level 15. This doesn't work if any code in an NMI handler does local_irq_save() or local_irq_disable() since the "disable" will kick us back to cpu IRQ level 14 thus letting NMIs back in and we recurse. The only path which that does that in the perf event IRQ handling path is the code supporting frequency based events. It uses cpu_clock(). cpu_clock() simply invokes sched_clock() with IRQs disabled. And that's a fundamental bug all on it's own, particularly for the HAVE_UNSTABLE_SCHED_CLOCK case. NMIs can thus get into the sched_clock() code interrupting the local IRQ disable code sections of it. Furthermore, for the not-HAVE_UNSTABLE_SCHED_CLOCK case, the IRQ disabling done by cpu_clock() is just pure overhead and completely unnecessary. So the core problem is that sched_clock() is not NMI safe, but we are invoking it from NMI contexts in the perf events code (via cpu_clock()). A less important issue is the overhead of IRQ disabling when it isn't necessary in cpu_clock(). CONFIG_HAVE_UNSTABLE_SCHED_CLOCK architectures are not affected by this patch. Signed-off-by: David S. Miller <davem@davemloft.net> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Mike Galbraith <efault@gmx.de> LKML-Reference: <20091213.182502.215092085.davem@davemloft.net> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Commit def0a9b2573 (sched_clock: Make it NMI safe) assumed cmpxchg() of 64bit values was available on X86_32. That is not so - and causes some subtle scheduler misbehavior due to incorrect timestamps off to up by ~4 seconds. Two symptoms are known right now: - interactivity problems seen by Arjan: up to 600 msecs latencies instead of the expected 20-40 msecs. These latencies are very visible on the desktop. - incorrect CPU stats: occasionally too high percentages in 'top', and crazy CPU usage stats. Reported-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: Arjan van de Ven <arjan@linux.intel.com> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: John Stultz <johnstul@us.ibm.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <20090930170754.0886ff2e@infradead.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Arjan complained about the suckyness of TSC on modern machines, and asked if we could do something about that for PERF_SAMPLE_TIME. Make cpu_clock() NMI safe by removing the spinlock and using cmpxchg. This also makes it smaller and more robust. Affects architectures that use HAVE_UNSTABLE_SCHED_CLOCK, i.e. IA64 and x86. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Account for the initial offset to the jiffy count. [ Impact: fix printk timestamps on architectures using fallback sched_clock() ] Signed-off-by: Ron Lee <ron@debian.org> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Conflicts: include/linux/slub_def.h lib/Kconfig.debug mm/slob.c mm/slub.c
Conflicts: kernel/sched_clock.c
- remove superfluous checks in __update_sched_clock() - skip sched_clock_tick() for sched_clock_stable - reinstate the simple !HAVE_UNSTABLE_SCHED_CLOCK code to please the bloatwatch Signed-off-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Allow CONFIG_HAVE_UNSTABLE_SCHED_CLOCK architectures to still specify that their sched_clock() implementation is reliable. This will be used by x86 to switch on a faster sched_clock_cpu() implementation on certain CPU types. Signed-off-by: Ingo Molnar <mingo@elte.hu>
make sure we dont execute more complex sched_clock() code in NMI context. Acked-by: Peter Zijlstra <peterz@infradead.org> Acked-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>