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FromKOSAKI Motohiro <>
Subject[PATCH 3/8] Don't use sleep_on()
DateMon, 14 Dec 2009 21:29:28 +0900 (JST)
sleep_on() is SMP and/or kernel preemption unsafe. This patch
replace it with safe code.

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
---
mm/vmscan.c | 40 ++++++++++++++++++++++++++++++----------
1 files changed, 30 insertions(+), 10 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 74c36fe..3be5345 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1599,15 +1599,32 @@ static unsigned long nr_scan_try_batch(unsigned long nr_to_scan,

static int shrink_zone_begin(struct zone *zone, struct scan_control *sc)
{
- if (!current_is_kswapd() &&
- atomic_read(&zone->concurrent_reclaimers) > max_zone_concurrent_reclaimers &&
- (sc->gfp_mask & (__GFP_IO|__GFP_FS)) == (__GFP_IO|__GFP_FS)) {
- /*
- * Do not add to the lock contention if this zone has
- * enough processes doing page reclaim already, since
- * we would just make things slower.
- */
- sleep_on(&zone->reclaim_wait);
+ DEFINE_WAIT(wait);
+ wait_queue_head_t *wq = &zone->reclaim_wait;
+
+ if (current_is_kswapd())
+ goto out;
+
+ /*
+ * GFP_NOIO and GFP_NOFS mean caller may have some lock implicitly.
+ * Thus, we can't wait here. otherwise it might cause deadlock.
+ */
+ if ((sc->gfp_mask & (__GFP_IO|__GFP_FS)) != (__GFP_IO|__GFP_FS))
+ goto out;
+
+ /*
+ * Do not add to the lock contention if this zone has
+ * enough processes doing page reclaim already, since
+ * we would just make things slower.
+ */
+ for (;;) {
+ prepare_to_wait(wq, &wait, TASK_UNINTERRUPTIBLE);
+
+ if (atomic_read(&zone->concurrent_reclaimers) <=
+ max_zone_concurrent_reclaimers)
+ break;
+
+ schedule();

/*
* If other processes freed enough memory while we waited,
@@ -1615,12 +1632,15 @@ static int shrink_zone_begin(struct zone *zone, struct scan_control *sc)
*/
if (zone_watermark_ok(zone, sc->order, low_wmark_pages(zone),
0, 0)) {
- wake_up(&zone->reclaim_wait);
+ wake_up(wq);
+ finish_wait(wq, &wait);
sc->nr_reclaimed += sc->nr_to_reclaim;
return -ERESTARTSYS;
}
}
+ finish_wait(wq, &wait);

+ out:
atomic_inc(&zone->concurrent_reclaimers);
return 0;
}
--
1.6.5.2




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