linux-kernel - [patch] epoll drop unnecessary test

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Message-ID: <Pine.LNX.4.64.0810011129260.20243@alien.or.mcafeemobile.com>
Date:	Wed, 1 Oct 2008 11:41:58 -0700 (PDT)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [patch] epoll drop unnecessary test

Thomas found that there is an unnecessary (always true) test in 
ep_send_events(). The callback never inserts into ->rdllink while the 
send loop is performed, and also does the ~EP_PRIVATE_BITS test. Given 
we're holding the mutex during this time, the conditions tested inside the 
loop are always true.
This patch drops the test done inside the re-insertion loop.


Signed-off-by: Davide Libenzi <davidel@...ilserver.org>



- Davide


---
 fs/eventpoll.c |    9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

Index: linux-2.6.mod/fs/eventpoll.c
===================================================================
--- linux-2.6.mod.orig/fs/eventpoll.c	2008-10-01 11:25:17.000000000 -0700
+++ linux-2.6.mod/fs/eventpoll.c	2008-10-01 11:26:58.000000000 -0700
@@ -927,14 +927,11 @@
 	/*
 	 * During the time we spent in the loop above, some other events
 	 * might have been queued by the poll callback. We re-insert them
-	 * here (in case they are not already queued, or they're one-shot).
+	 * inside the main ready-list here.
 	 */
 	for (nepi = ep->ovflist; (epi = nepi) != NULL;
-	     nepi = epi->next, epi->next = EP_UNACTIVE_PTR) {
-		if (!ep_is_linked(&epi->rdllink) &&
-		    (epi->event.events & ~EP_PRIVATE_BITS))
-			list_add_tail(&epi->rdllink, &ep->rdllist);
-	}
+	     nepi = epi->next, epi->next = EP_UNACTIVE_PTR)
+		list_add_tail(&epi->rdllink, &ep->rdllist);
 	/*
 	 * We need to set back ep->ovflist to EP_UNACTIVE_PTR, so that after
 	 * releasing the lock, events will be queued in the normal way inside

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