xtime_lock vs update_process_times
Commit d3d74453c3
("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>
This commit is contained in:
parent
10270d4838
commit
aa02cd2d9b
@ -119,13 +119,8 @@ irqreturn_t timer_interrupt(int irq, void *dev)
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state.partial_tick = delta & ((1UL << FIX_SHIFT) - 1);
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nticks = delta >> FIX_SHIFT;
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while (nticks > 0) {
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do_timer(1);
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#ifndef CONFIG_SMP
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update_process_times(user_mode(get_irq_regs()));
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#endif
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nticks--;
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}
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if (nticks)
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do_timer(nticks);
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/*
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* If we have an externally synchronized Linux clock, then update
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@ -141,6 +136,12 @@ irqreturn_t timer_interrupt(int irq, void *dev)
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}
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write_sequnlock(&xtime_lock);
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#ifndef CONFIG_SMP
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while (nticks--)
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update_process_times(user_mode(get_irq_regs()));
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#endif
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return IRQ_HANDLED;
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}
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@ -137,9 +137,6 @@ irqreturn_t timer_interrupt(int irq, void *dummy)
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do_timer(1);
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#ifndef CONFIG_SMP
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update_process_times(user_mode(get_irq_regs()));
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#endif
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profile_tick(CPU_PROFILING);
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/*
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@ -161,6 +158,11 @@ irqreturn_t timer_interrupt(int irq, void *dummy)
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last_rtc_update = xtime.tv_sec - 600;
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}
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write_sequnlock(&xtime_lock);
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#ifndef CONFIG_SMP
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update_process_times(user_mode(get_irq_regs()));
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#endif
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return IRQ_HANDLED;
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}
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@ -63,6 +63,7 @@ static irqreturn_t timer_interrupt(int irq, void *dummy)
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/* last time the cmos clock got updated */
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static long last_rtc_update = 0;
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profile_tick(CPU_PROFILING);
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/*
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* Here we are in the timer irq handler. We just have irqs locally
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* disabled but we don't know if the timer_bh is running on the other
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@ -73,8 +74,6 @@ static irqreturn_t timer_interrupt(int irq, void *dummy)
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write_seqlock(&xtime_lock);
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do_timer(1);
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update_process_times(user_mode(get_irq_regs()));
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profile_tick(CPU_PROFILING);
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/*
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* If we have an externally synchronized Linux clock, then update
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@ -99,6 +98,9 @@ static irqreturn_t timer_interrupt(int irq, void *dummy)
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#endif /* CONFIG_HEARTBEAT */
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write_sequnlock(&xtime_lock);
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update_process_times(user_mode(get_irq_regs()));
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return IRQ_HANDLED;
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}
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@ -42,14 +42,12 @@ irqreturn_t arch_timer_interrupt(int irq, void *dummy)
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/* last time the cmos clock got updated */
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static long last_rtc_update=0;
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if (current->pid)
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profile_tick(CPU_PROFILING);
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write_seqlock(&xtime_lock);
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do_timer(1);
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#ifndef CONFIG_SMP
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update_process_times(user_mode(get_irq_regs()));
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#endif
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if (current->pid)
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profile_tick(CPU_PROFILING);
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/*
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* If we have an externally synchronized Linux clock, then update
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@ -67,6 +65,10 @@ irqreturn_t arch_timer_interrupt(int irq, void *dummy)
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}
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write_sequnlock(&xtime_lock);
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#ifndef CONFIG_SMP
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update_process_times(user_mode(get_irq_regs()));
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#endif
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return(IRQ_HANDLED);
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}
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@ -100,16 +100,7 @@ static irqreturn_t cmt_timer_interrupt(int irq, void *dev_id)
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timer_status &= ~0x80;
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ctrl_outw(timer_status, CMT_CMCSR_0);
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/*
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* Here we are in the timer irq handler. We just have irqs locally
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* disabled but we don't know if the timer_bh is running on the other
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* CPU. We need to avoid to SMP race with it. NOTE: we don' t need
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* the irq version of write_lock because as just said we have irq
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* locally disabled. -arca
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*/
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write_seqlock(&xtime_lock);
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handle_timer_tick();
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write_sequnlock(&xtime_lock);
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return IRQ_HANDLED;
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}
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@ -100,9 +100,7 @@ static irqreturn_t mtu2_timer_interrupt(int irq, void *dev_id)
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ctrl_outb(timer_status, MTU2_TSR_1);
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/* Do timer tick */
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write_seqlock(&xtime_lock);
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handle_timer_tick();
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write_sequnlock(&xtime_lock);
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return IRQ_HANDLED;
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}
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@ -713,10 +713,10 @@ static irqreturn_t pcic_timer_handler (int irq, void *h)
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write_seqlock(&xtime_lock); /* Dummy, to show that we remember */
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pcic_clear_clock_irq();
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do_timer(1);
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write_sequnlock(&xtime_lock);
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#ifndef CONFIG_SMP
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update_process_times(user_mode(get_irq_regs()));
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#endif
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write_sequnlock(&xtime_lock);
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return IRQ_HANDLED;
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}
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@ -128,10 +128,6 @@ irqreturn_t timer_interrupt(int irq, void *dev_id)
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clear_clock_irq();
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do_timer(1);
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#ifndef CONFIG_SMP
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update_process_times(user_mode(get_irq_regs()));
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#endif
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/* Determine when to update the Mostek clock. */
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if (ntp_synced() &&
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@ -145,6 +141,9 @@ irqreturn_t timer_interrupt(int irq, void *dev_id)
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}
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write_sequnlock(&xtime_lock);
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#ifndef CONFIG_SMP
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update_process_times(user_mode(get_irq_regs()));
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#endif
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return IRQ_HANDLED;
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}
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