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/sh/kernel/timers/timer-cmt.c | 9 --------- arch/sh/kernel/timers/timer-mtu2.c | 2 -- 2 files changed, 11 deletions(-) (limited to 'arch/sh') diff --git a/arch/sh/kernel/timers/timer-cmt.c b/arch/sh/kernel/timers/timer-cmt.c index 499e07beebe..71312324b5d 100644 --- a/arch/sh/kernel/timers/timer-cmt.c +++ b/arch/sh/kernel/timers/timer-cmt.c @@ -100,16 +100,7 @@ static irqreturn_t cmt_timer_interrupt(int irq, void *dev_id) timer_status &= ~0x80; ctrl_outw(timer_status, CMT_CMCSR_0); - /* - * 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 - * CPU. We need to avoid to SMP race with it. NOTE: we don' t need - * the irq version of write_lock because as just said we have irq - * locally disabled. -arca - */ - write_seqlock(&xtime_lock); handle_timer_tick(); - write_sequnlock(&xtime_lock); return IRQ_HANDLED; } diff --git a/arch/sh/kernel/timers/timer-mtu2.c b/arch/sh/kernel/timers/timer-mtu2.c index b7499a2a918..463cd08f951 100644 --- a/arch/sh/kernel/timers/timer-mtu2.c +++ b/arch/sh/kernel/timers/timer-mtu2.c @@ -100,9 +100,7 @@ static irqreturn_t mtu2_timer_interrupt(int irq, void *dev_id) ctrl_outb(timer_status, MTU2_TSR_1); /* Do timer tick */ - write_seqlock(&xtime_lock); handle_timer_tick(); - write_sequnlock(&xtime_lock); return IRQ_HANDLED; } -- cgit v1.2.3