From: Paul E. McKenney Date: Thu, 28 Feb 2008 19:51:07 +0000 (-0800) Subject: rcupreempt: remove never-migrates assumption from rcu_process_callbacks() X-Git-Tag: v2.6.25-rc4~129 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c9e71002aacc9821e99531dcc130db88bbc8ad05;p=linux-2.6 rcupreempt: remove never-migrates assumption from rcu_process_callbacks() This patch fixes a potentially invalid access to a per-CPU variable in rcu_process_callbacks(). This per-CPU access needs to be done in such a way as to guarantee that the code using it cannot move to some other CPU before all uses of the value accessed have completed. Even though this code is currently only invoked from softirq context, which currrently cannot migrate to some other CPU, life would be better if this code did not silently make such an assumption. Signed-off-by: Paul E. McKenney Signed-off-by: Ingo Molnar --- diff --git a/kernel/rcupreempt.c b/kernel/rcupreempt.c index 845abcd472..e9517014b5 100644 --- a/kernel/rcupreempt.c +++ b/kernel/rcupreempt.c @@ -952,9 +952,11 @@ static void rcu_process_callbacks(struct softirq_action *unused) { unsigned long flags; struct rcu_head *next, *list; - struct rcu_data *rdp = RCU_DATA_ME(); + struct rcu_data *rdp; - spin_lock_irqsave(&rdp->lock, flags); + local_irq_save(flags); + rdp = RCU_DATA_ME(); + spin_lock(&rdp->lock); list = rdp->donelist; if (list == NULL) { spin_unlock_irqrestore(&rdp->lock, flags);