linux-kernel - [PATCH] rcu_do_batch: make ->qlen decrement irq safe

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Date:	Mon, 11 Sep 2006 01:32:43 +0400
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Dipankar Sarma <dipankar@...ibm.com>
Cc:	"Paul E. McKenney" <paulmck@...ibm.com>,
	Srivatsa Vaddagiri <vatsa@...ibm.com>,
	Andrew Morton <akpm@...l.org>, linux-kernel@...r.kernel.org
Subject: [PATCH] rcu_do_batch: make ->qlen decrement irq safe

rcu_do_batch() decrements rdp->qlen with irqs enabled. This is not good,
it can also be modified by call_rcu() from interrupt.

Decrement ->qlen once with irqs disabled, after a main loop.

Signed-off-by: Oleg Nesterov <oleg@...sign.ru>

--- rc6-mm1/kernel/rcupdate.c~	2006-08-22 16:22:49.000000000 +0400
+++ rc6-mm1/kernel/rcupdate.c	2006-09-11 01:24:17.000000000 +0400
@@ -241,12 +241,16 @@ static void rcu_do_batch(struct rcu_data
 		next = rdp->donelist = list->next;
 		list->func(list);
 		list = next;
-		rdp->qlen--;
 		if (++count >= rdp->blimit)
 			break;
 	}
+
+	local_irq_disable();
+	rdp->qlen -= count;
+	local_irq_enable();
 	if (rdp->blimit == INT_MAX && rdp->qlen <= qlowmark)
 		rdp->blimit = blimit;
+
 	if (!rdp->donelist)
 		rdp->donetail = &rdp->donelist;
 	else

-
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