From aa02cd2d9bd1e24a230bd66a0a741b984d03915a Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 13 Feb 2008 21:33:16 +0100 Subject: xtime_lock vs update_process_times Commit d3d74453c34f8fd87674a8cf5b8a327c68f22e99 ("hrtimer: fixup the HRTIMER_CB_IRQSAFE_NO_SOFTIRQ fallback") broke several archs, and since only Russell bothered to merge the fix, and Greg to ACK his arch, I'm sending this for merger. I have confirmation that the Alpha bit results in a booting kernel. That leaves: blackfin, frv, sh and sparc untested. The deadlock in question was found by Russell: IRQ handle -> timer_tick() - xtime seqlock held for write -> update_process_times() -> run_local_timers() -> hrtimer_run_queues() -> hrtimer_get_softirq_time() - tries to get a read lock Now, Thomas assures me the fix is trivial, only do_timer() needs to be done under the xtime_lock, and update_process_times() can savely be removed from under it. Signed-off-by: Peter Zijlstra Acked-by: Greg Ungerer CC: Richard Henderson CC: Bryan Wu CC: David Howells CC: Paul Mundt CC: William Irwin Acked-by: Ingo Molnar Acked-by: Ivan Kokshaysky Signed-off-by: Linus Torvalds --- arch/m68knommu/kernel/time.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) (limited to 'arch/m68knommu') diff --git a/arch/m68knommu/kernel/time.c b/arch/m68knommu/kernel/time.c index 89cdbcaeb45..0ccfb2ad638 100644 --- a/arch/m68knommu/kernel/time.c +++ b/arch/m68knommu/kernel/time.c @@ -42,14 +42,12 @@ irqreturn_t arch_timer_interrupt(int irq, void *dummy) /* last time the cmos clock got updated */ static long last_rtc_update=0; + if (current->pid) + profile_tick(CPU_PROFILING); + write_seqlock(&xtime_lock); do_timer(1); -#ifndef CONFIG_SMP - update_process_times(user_mode(get_irq_regs())); -#endif - if (current->pid) - profile_tick(CPU_PROFILING); /* * If we have an externally synchronized Linux clock, then update @@ -67,6 +65,10 @@ irqreturn_t arch_timer_interrupt(int irq, void *dummy) } write_sequnlock(&xtime_lock); + +#ifndef CONFIG_SMP + update_process_times(user_mode(get_irq_regs())); +#endif return(IRQ_HANDLED); } -- cgit v1.2.3-18-g5258