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SubjectRe: Regression: WARNINGS and lockdep spews in 2.6.38-rc3+ (bisected).
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Date

How about we revert your patch and go back to not allowing
del_timer_sync() from any interrupt context, we can fix __dst_free by
removing the need for cancel_delayed_work().

Are there any other del_timer_sync() callers from softirq?

---
include/linux/timer.h | 1 +
kernel/timer.c | 67 ++++++++++++++++++++++++++++++------------------
kernel/workqueue.c | 4 +-
net/core/dst.c | 1 -
4 files changed, 45 insertions(+), 28 deletions(-)
diff --git a/include/linux/timer.h b/include/linux/timer.h
index 6abd913..3e263f9 100644
--- a/include/linux/timer.h
+++ b/include/linux/timer.h
@@ -209,6 +209,7 @@ static inline int timer_pending(const struct timer_list * timer)
extern void add_timer_on(struct timer_list *timer, int cpu);
extern int del_timer(struct timer_list * timer);
extern int mod_timer(struct timer_list *timer, unsigned long expires);
+extern int mod_timer_on(struct timer_list *timer, unsigned long expires, int cpu);
extern int mod_timer_pending(struct timer_list *timer, unsigned long expires);
extern int mod_timer_pinned(struct timer_list *timer, unsigned long expires);

diff --git a/kernel/timer.c b/kernel/timer.c
index 87f656c..c9e98f7 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -648,8 +648,8 @@ static struct tvec_base *lock_timer_base(struct timer_list *timer,
}

static inline int
-__mod_timer(struct timer_list *timer, unsigned long expires,
- bool pending_only, int pinned)
+__mod_timer_on(struct timer_list *timer, unsigned long expires,
+ bool pending_only, int pinned, int cpu)
{
struct tvec_base *base, *new_base;
unsigned long flags;
@@ -673,12 +673,14 @@ __mod_timer(struct timer_list *timer, unsigned long expires,

debug_activate(timer, expires);

- cpu = smp_processor_id();
+ if (cpu == -1) {
+ cpu = smp_processor_id();

#if defined(CONFIG_NO_HZ) && defined(CONFIG_SMP)
- if (!pinned && get_sysctl_timer_migration() && idle_cpu(cpu))
- cpu = get_nohz_timer_target();
+ if (!pinned && get_sysctl_timer_migration() && idle_cpu(cpu))
+ cpu = get_nohz_timer_target();
#endif
+ }
new_base = per_cpu(tvec_bases, cpu);

if (base != new_base) {
@@ -705,12 +707,30 @@ __mod_timer(struct timer_list *timer, unsigned long expires,
base->next_timer = timer->expires;
internal_add_timer(base, timer);

+ if (cpu != smp_processor_id()) {
+ /*
+ * Check whether the other CPU is idle and needs to be
+ * triggered to reevaluate the timer wheel when nohz is
+ * active. We are protected against the other CPU fiddling
+ * with the timer by holding the timer base lock. This also
+ * makes sure that a CPU on the way to idle can not evaluate
+ * the timer wheel.
+ */
+ wake_up_idle_cpu(cpu);
+ }
out_unlock:
spin_unlock_irqrestore(&base->lock, flags);

return ret;
}

+static inline int
+__mod_timer(struct timer_list *timer, unsigned long expires,
+ bool pending_only, int pinned)
+{
+ return __mod_timer_on(timer, expires, pending_only, pinned, -1);
+}
+
/**
* mod_timer_pending - modify a pending timer's timeout
* @timer: the pending timer to be modified
@@ -825,6 +845,17 @@ int mod_timer_pinned(struct timer_list *timer, unsigned long expires)
}
EXPORT_SYMBOL(mod_timer_pinned);

+int mod_timer_on(struct timer_list *timer, unsigned long expires, int cpu)
+{
+ if (timer_pending(timer) && timer->expires == expires)
+ return 1;
+
+ expires = apply_slack(timer, expires);
+
+ return __mod_timer_on(timer, expires, false, TIMER_NOT_PINNED, cpu);
+}
+EXPORT_SYMBOL(mod_timer_on);
+
/**
* add_timer - start a timer
* @timer: the timer to be added
@@ -860,23 +891,7 @@ void add_timer_on(struct timer_list *timer, int cpu)

timer_stats_timer_set_start_info(timer);
BUG_ON(timer_pending(timer) || !timer->function);
- spin_lock_irqsave(&base->lock, flags);
- timer_set_base(timer, base);
- debug_activate(timer, timer->expires);
- if (time_before(timer->expires, base->next_timer) &&
- !tbase_get_deferrable(timer->base))
- base->next_timer = timer->expires;
- internal_add_timer(base, timer);
- /*
- * Check whether the other CPU is idle and needs to be
- * triggered to reevaluate the timer wheel when nohz is
- * active. We are protected against the other CPU fiddling
- * with the timer by holding the timer base lock. This also
- * makes sure that a CPU on the way to idle can not evaluate
- * the timer wheel.
- */
- wake_up_idle_cpu(cpu);
- spin_unlock_irqrestore(&base->lock, flags);
+ mod_timer_on(timer, timer->expires, cpu);
}
EXPORT_SYMBOL_GPL(add_timer_on);

@@ -959,7 +974,7 @@ EXPORT_SYMBOL(try_to_del_timer_sync);
*
* Synchronization rules: Callers must prevent restarting of the timer,
* otherwise this function is meaningless. It must not be called from
- * hardirq contexts. The caller must not hold locks which would prevent
+ * interrupt contexts. The caller must not hold locks which would prevent
* completion of the timer's handler. The timer's handler must not call
* add_timer_on(). Upon exit the timer is not queued and the handler is
* not running on any CPU.
@@ -969,10 +984,12 @@ EXPORT_SYMBOL(try_to_del_timer_sync);
int del_timer_sync(struct timer_list *timer)
{
#ifdef CONFIG_LOCKDEP
- local_bh_disable();
+ unsigned long flags;
+
+ local_irq_save(flags);
lock_map_acquire(&timer->lockdep_map);
lock_map_release(&timer->lockdep_map);
- local_bh_enable();
+ local_irq_restore(flags);
#endif
/*
* don't use it in hardirq context, because it
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 11869fa..3944acc 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1160,9 +1160,9 @@ int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
timer->function = delayed_work_timer_fn;

if (unlikely(cpu >= 0))
- add_timer_on(timer, cpu);
+ mod_timer_on(timer, cpu);
else
- add_timer(timer);
+ mod_timer(timer);
ret = 1;
}
return ret;
diff --git a/net/core/dst.c b/net/core/dst.c
index b99c7c7..a4f28bc 100644
--- a/net/core/dst.c
+++ b/net/core/dst.c
@@ -207,7 +207,6 @@ void __dst_free(struct dst_entry *dst)
if (dst_garbage.timer_inc > DST_GC_INC) {
dst_garbage.timer_inc = DST_GC_INC;
dst_garbage.timer_expires = DST_GC_MIN;
- cancel_delayed_work(&dst_gc_work);
schedule_delayed_work(&dst_gc_work, dst_garbage.timer_expires);
}
spin_unlock_bh(&dst_garbage.lock);



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