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Date: Mon, 19 Jul 2004 12:20:30 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Zwane Mwaikambo <zwane@linuxpower.ca>
Cc: Arjan van de Ven <arjanv@redhat.com>, Andrew Morton <akpm@osdl.org>,
       Linux Kernel <linux-kernel@vger.kernel.org>,
       linux-audio-dev@music.columbia.edu
Subject: Re: [announce] [patch] Voluntary Kernel Preemption Patch
Message-ID: <20040719102030.GA5046@elte.hu>
References: <20040709182638.GA11310@elte.hu> <20040710222510.0593f4a4.akpm@osdl.org> <20040711093209.GA17095@elte.hu> <20040711024518.7fd508e0.akpm@osdl.org> <20040711095039.GA22391@elte.hu> <20040711025855.08afbca1.akpm@osdl.org> <20040711103020.GA24797@elte.hu> <20040711034258.796f8c6a.akpm@osdl.org> <20040711105936.GA13956@devserv.devel.redhat.com> <Pine.LNX.4.58.0407120300200.23212@montezuma.fsmlabs.com>
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* Zwane Mwaikambo <zwane@linuxpower.ca> wrote:

> Looks like some of the voluntary preemption changes might need some
> eyeballing too. This appears to be a use after free, probably since we
> unlocked j_{list,state}_lock.

thx - this is the new __journal_clean_checkpoint_list() chunk:

--- linux/fs/jbd/checkpoint.c.orig	
+++ linux/fs/jbd/checkpoint.c	
@@ -465,6 +470,7 @@ int __journal_clean_checkpoint_list(jour
 	transaction_t *transaction, *last_transaction, *next_transaction;
 	int ret = 0;
 
+retry:
 	transaction = journal->j_checkpoint_transactions;
 	if (transaction == 0)
 		goto out;
@@ -487,6 +493,14 @@ int __journal_clean_checkpoint_list(jour
 				/* Use trylock because of the ranknig */
 				if (jbd_trylock_bh_state(jh2bh(jh)))
 					ret += __try_to_free_cp_buf(jh);
+				if (voluntary_need_resched()) {
+					spin_unlock(&journal->j_list_lock);
+					spin_unlock(&journal->j_state_lock);
+					voluntary_resched();
+					spin_lock(&journal->j_state_lock);
+					spin_lock(&journal->j_list_lock);
+					goto retry;
+				}
 			} while (jh != last_jh);
 		}
 	} while (transaction != last_transaction);