The patch titled
xtime_lock vs update_process_times
has been added to the -mm tree. Its filename is
xtime_lock-vs-update_process_times.patch
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out what to do about this
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: xtime_lock vs update_process_times
From: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Commit: d3d74453c34f8fd87674a8cf5b8a327c68f22e99
Subject: hrtimer: fixup the HRTIMER_CB_IRQSAFE_NO_SOFTIRQ fallback
Broke several archs. 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@xxxxxxxxx>
Acked-by: Greg Ungerer <gerg@xxxxxxxxxxx>
Cc: Richard Henderson <rth@xxxxxxxxxxx>
Tested-by: Ivan Kokshaysky <ink@xxxxxxxxxxxxxxxxxxxx>
Cc: Bryan Wu <bryan.wu@xxxxxxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: Paul Mundt <lethal@xxxxxxxxxxxx>
Cc: William Lee Irwin III <wli@xxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/alpha/kernel/time.c | 15 ++++++++-------
arch/blackfin/kernel/time.c | 8 +++++---
arch/frv/kernel/time.c | 6 ++++--
arch/m68knommu/kernel/time.c | 12 +++++++-----
arch/sparc/kernel/pcic.c | 2 +-
arch/sparc/kernel/time.c | 7 +++----
6 files changed, 28 insertions(+), 22 deletions(-)
diff -puN arch/alpha/kernel/time.c~xtime_lock-vs-update_process_times arch/alpha/kernel/time.c
--- a/arch/alpha/kernel/time.c~xtime_lock-vs-update_process_times
+++ a/arch/alpha/kernel/time.c
@@ -119,13 +119,8 @@ irqreturn_t timer_interrupt(int irq, voi
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, voi
}
write_sequnlock(&xtime_lock);
+
+#ifndef CONFIG_SMP
+ while (nticks--)
+ update_process_times(user_mode(get_irq_regs()));
+#endif
+
return IRQ_HANDLED;
}
diff -puN arch/blackfin/kernel/time.c~xtime_lock-vs-update_process_times arch/blackfin/kernel/time.c
--- a/arch/blackfin/kernel/time.c~xtime_lock-vs-update_process_times
+++ a/arch/blackfin/kernel/time.c
@@ -137,9 +137,6 @@ irqreturn_t timer_interrupt(int irq, voi
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, voi
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;
}
diff -puN arch/frv/kernel/time.c~xtime_lock-vs-update_process_times arch/frv/kernel/time.c
--- a/arch/frv/kernel/time.c~xtime_lock-vs-update_process_times
+++ a/arch/frv/kernel/time.c
@@ -63,6 +63,7 @@ static irqreturn_t timer_interrupt(int i
/* 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 i
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 i
#endif /* CONFIG_HEARTBEAT */
write_sequnlock(&xtime_lock);
+
+ update_process_times(user_mode(get_irq_regs()));
+
return IRQ_HANDLED;
}
diff -puN arch/m68knommu/kernel/time.c~xtime_lock-vs-update_process_times arch/m68knommu/kernel/time.c
--- a/arch/m68knommu/kernel/time.c~xtime_lock-vs-update_process_times
+++ a/arch/m68knommu/kernel/time.c
@@ -42,14 +42,12 @@ irqreturn_t arch_timer_interrupt(int irq
/* 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
}
write_sequnlock(&xtime_lock);
+
+#ifndef CONFIG_SMP
+ update_process_times(user_mode(get_irq_regs()));
+#endif
return(IRQ_HANDLED);
}
diff -puN arch/sparc/kernel/pcic.c~xtime_lock-vs-update_process_times arch/sparc/kernel/pcic.c
--- a/arch/sparc/kernel/pcic.c~xtime_lock-vs-update_process_times
+++ a/arch/sparc/kernel/pcic.c
@@ -713,10 +713,10 @@ static irqreturn_t pcic_timer_handler (i
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;
}
diff -puN arch/sparc/kernel/time.c~xtime_lock-vs-update_process_times arch/sparc/kernel/time.c
--- a/arch/sparc/kernel/time.c~xtime_lock-vs-update_process_times
+++ a/arch/sparc/kernel/time.c
@@ -128,10 +128,6 @@ irqreturn_t timer_interrupt(int irq, voi
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, voi
}
write_sequnlock(&xtime_lock);
+#ifndef CONFIG_SMP
+ update_process_times(user_mode(get_irq_regs()));
+#endif
return IRQ_HANDLED;
}
_
Patches currently in -mm which might be from a.p.zijlstra@xxxxxxxxx are
origin.patch
softlockup-workaround.patch
git-sched.patch
git-sh.patch
git-x86.patch
proc-add-rlimit_rttime-to-proc-pid-limits.patch
xtime_lock-vs-update_process_times.patch
mm-bdi-export-bdi-attributes-in-sysfs.patch
mm-bdi-expose-the-bdi-object-in-sysfs-for-nfs.patch
mm-bdi-expose-the-bdi-object-in-sysfs-for-fuse.patch
mm-bdi-allow-setting-a-minimum-for-the-bdi-dirty-limit.patch
mm-bdi-allow-setting-a-maximum-for-the-bdi-dirty-limit.patch
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