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/frv/kernel/time.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'arch/frv') diff --git a/arch/frv/kernel/time.c b/arch/frv/kernel/time.c index 925fb0199a0..69f6a4ef5d6 100644 --- a/arch/frv/kernel/time.c +++ b/arch/frv/kernel/time.c @@ -63,6 +63,7 @@ static irqreturn_t timer_interrupt(int irq, void *dummy) /* last time the cmos clock got updated */ static long last_rtc_update = 0; + profile_tick(CPU_PROFILING); /* * Here we are in the timer irq handler. We just have irqs locally * disabled but we don't know if the timer_bh is running on the other @@ -73,8 +74,6 @@ static irqreturn_t timer_interrupt(int irq, void *dummy) write_seqlock(&xtime_lock); do_timer(1); - update_process_times(user_mode(get_irq_regs())); - profile_tick(CPU_PROFILING); /* * If we have an externally synchronized Linux clock, then update @@ -99,6 +98,9 @@ static irqreturn_t timer_interrupt(int irq, void *dummy) #endif /* CONFIG_HEARTBEAT */ write_sequnlock(&xtime_lock); + + update_process_times(user_mode(get_irq_regs())); + return IRQ_HANDLED; } -- cgit v1.2.3