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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2008-02-13 21:33:16 +0100
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-02-13 13:29:25 -0800
commitaa02cd2d9bd1e24a230bd66a0a741b984d03915a (patch)
tree06e341e095749048feabbe2ded236e5db38ee251 /arch/sh/kernel/timers
parent10270d4838bdc493781f5a1cf2e90e9c34c9142f (diff)
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 <a.p.zijlstra@chello.nl> Acked-by: Greg Ungerer <gerg@uclinux.org> CC: Richard Henderson <rth@twiddle.net> CC: Bryan Wu <bryan.wu@analog.com> CC: David Howells <dhowells@redhat.com> CC: Paul Mundt <lethal@linux-sh.org> CC: William Irwin <wli@holomorphy.com> Acked-by: Ingo Molnar <mingo@elte.hu> Acked-by: Ivan Kokshaysky <ink@jurassic.park.msu.ru> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/sh/kernel/timers')
-rw-r--r--arch/sh/kernel/timers/timer-cmt.c9
-rw-r--r--arch/sh/kernel/timers/timer-mtu2.c2
2 files changed, 0 insertions, 11 deletions
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;
}