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/alpha/kernel/time.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) (limited to 'arch/alpha') diff --git a/arch/alpha/kernel/time.c b/arch/alpha/kernel/time.c index 1dd50d07693..75480cab089 100644 --- a/arch/alpha/kernel/time.c +++ b/arch/alpha/kernel/time.c @@ -119,13 +119,8 @@ irqreturn_t timer_interrupt(int irq, void *dev) state.partial_tick = delta & ((1UL << FIX_SHIFT) - 1); nticks = delta >> FIX_SHIFT; - while (nticks > 0) { - do_timer(1); -#ifndef CONFIG_SMP - update_process_times(user_mode(get_irq_regs())); -#endif - nticks--; - } + if (nticks) + do_timer(nticks); /* * If we have an externally synchronized Linux clock, then update @@ -141,6 +136,12 @@ irqreturn_t timer_interrupt(int irq, void *dev) } write_sequnlock(&xtime_lock); + +#ifndef CONFIG_SMP + while (nticks--) + update_process_times(user_mode(get_irq_regs())); +#endif + return IRQ_HANDLED; } -- cgit v1.2.3