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Commit f0098f78 authored by Denis Lunev's avatar Denis Lunev Committed by David S. Miller
Browse files

[NET] Fix too aggressive backoff in dst garbage collection 



The bug is evident when it is seen once. dst gc timer was backed off,
when gc queue is not empty. But this means that timer quickly backs off,
if at least one destination remains in use. Normally, the bug is invisible,
because adding new dst entry to queue cancels the backoff. But it shots
deadly with destination cache overflow when new destinations are not released
for long time f.e. after an interface goes down.

The fix is to cancel backoff when something was released.

Signed-off-by: default avatarDenis Lunev <den@sw.ru>
Signed-off-by: default avatarAlexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent db44575f

net/core/dst.c

+11 −4
Original line number Diff line number Diff line
@@ -45,6 +45,7 @@ static struct timer_list dst_gc_timer = 
static void dst_run_gc(unsigned long dummy)

{

	int    delayed = 0;

	int    work_performed;

	struct dst_entry * dst, **dstp;



	if (!spin_trylock(&dst_lock)) {
@@ -52,9 +53,9 @@ static void dst_run_gc(unsigned long dummy) 
		return;

	}





	del_timer(&dst_gc_timer);

	dstp = &dst_garbage_list;

	work_performed = 0;

	while ((dst = *dstp) != NULL) {

		if (atomic_read(&dst->__refcnt)) {

			dstp = &dst->next;
@@ -62,6 +63,7 @@ static void dst_run_gc(unsigned long dummy) 
			continue;

		}

		*dstp = dst->next;

		work_performed = 1;



		dst = dst_destroy(dst);

		if (dst) {
@@ -86,9 +88,14 @@ static void dst_run_gc(unsigned long dummy) 
		dst_gc_timer_inc = DST_GC_MAX;

		goto out;

	}

	if (!work_performed) {

		if ((dst_gc_timer_expires += dst_gc_timer_inc) > DST_GC_MAX)

			dst_gc_timer_expires = DST_GC_MAX;

		dst_gc_timer_inc += DST_GC_INC;

	} else {

		dst_gc_timer_inc = DST_GC_INC;

		dst_gc_timer_expires = DST_GC_MIN;

	}

	dst_gc_timer.expires = jiffies + dst_gc_timer_expires;

#if RT_CACHE_DEBUG >= 2

	printk("dst_total: %d/%d %ld\n",