Commit aa02cd2d authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Linus Torvalds
Browse files

xtime_lock vs update_process_times

Commit d3d74453

 ("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: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: default avatarGreg 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: default avatarIngo Molnar <mingo@elte.hu>
Acked-by: default avatarIvan Kokshaysky <ink@jurassic.park.msu.ru>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 10270d48
......@@ -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;
}
......
......@@ -137,9 +137,6 @@ irqreturn_t timer_interrupt(int irq, void *dummy)
do_timer(1);
#ifndef CONFIG_SMP
update_process_times(user_mode(get_irq_regs()));
#endif
profile_tick(CPU_PROFILING);
/*
......@@ -161,6 +158,11 @@ irqreturn_t timer_interrupt(int irq, void *dummy)
last_rtc_update = xtime.tv_sec - 600;
}
write_sequnlock(&xtime_lock);
#ifndef CONFIG_SMP
update_process_times(user_mode(get_irq_regs()));
#endif
return IRQ_HANDLED;
}
......
......@@ -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;
}
......
......@@ -42,14 +42,12 @@ irqreturn_t arch_timer_interrupt(int irq, void *dummy)
/* last time the cmos clock got updated */
static long last_rtc_update=0;
if (current->pid)
profile_tick(CPU_PROFILING);
write_seqlock(&xtime_lock);
do_timer(1);
#ifndef CONFIG_SMP
update_process_times(user_mode(get_irq_regs()));
#endif
if (current->pid)
profile_tick(CPU_PROFILING);
/*
* If we have an externally synchronized Linux clock, then update
......@@ -67,6 +65,10 @@ irqreturn_t arch_timer_interrupt(int irq, void *dummy)
}
write_sequnlock(&xtime_lock);
#ifndef CONFIG_SMP
update_process_times(user_mode(get_irq_regs()));
#endif
return(IRQ_HANDLED);
}
......
......@@ -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;
}
......
......@@ -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;
}
......
......@@ -713,10 +713,10 @@ static irqreturn_t pcic_timer_handler (int irq, void *h)
write_seqlock(&xtime_lock); /* Dummy, to show that we remember */
pcic_clear_clock_irq();
do_timer(1);
write_sequnlock(&xtime_lock);
#ifndef CONFIG_SMP
update_process_times(user_mode(get_irq_regs()));
#endif
write_sequnlock(&xtime_lock);
return IRQ_HANDLED;
}
......
......@@ -128,10 +128,6 @@ irqreturn_t timer_interrupt(int irq, void *dev_id)
clear_clock_irq();
do_timer(1);
#ifndef CONFIG_SMP
update_process_times(user_mode(get_irq_regs()));
#endif
/* Determine when to update the Mostek clock. */
if (ntp_synced() &&
......@@ -145,6 +141,9 @@ irqreturn_t timer_interrupt(int irq, void *dev_id)
}
write_sequnlock(&xtime_lock);
#ifndef CONFIG_SMP
update_process_times(user_mode(get_irq_regs()));
#endif
return IRQ_HANDLED;
}
......
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