On Thu, Sep 09, 2010 at 01:13:22PM +0900, KOSAKI Motohiro wrote: > > On Thu, 9 Sep 2010 12:04:48 +0900 > > KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote: > > > > > On Mon, 6 Sep 2010 11:47:28 +0100 > > > Mel Gorman <mel@xxxxxxxxx> wrote: > > > > > > > From: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> > > > > > > > > With synchrounous lumpy reclaim, there is no reason to give up to reclaim > > > > pages even if page is locked. This patch uses lock_page() instead of > > > > trylock_page() in this case. > > > > > > > > Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> > > > > Signed-off-by: Mel Gorman <mel@xxxxxxxxx> > > > > > > Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> > > > > > Ah......but can't this change cause dead lock ?? > > Yes, this patch is purely crappy. please drop. I guess I was poisoned > by poisonous mushroom of Mario Bros. > Lets be clear on what the exact dead lock conditions are. The ones I had thought about when I felt this patch was ok were; o We are not holding the LRU lock (or any lock, we just called cond_resched()) o We do not have another page locked because we cannot lock multiple pages o Kswapd will never be in LUMPY_MODE_SYNC so it is not getting blocked o lock_page() itself is not allocating anything that we could recurse on One potential dead lock would be if the direct reclaimer held a page lock and ended up here but is that situation even allowed? I did not think of an obvious example of when this would happen. Similarly, deadlock situations with mmap_sem shouldn't happen unless multiple page locks are being taken. (prepares to feel foolish) What did I miss? -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
