Messages in this thread Patch in this message | | | Date | Thu, 28 Feb 2008 11:51:07 -0800 | From | "Paul E. McKenney" <> | Subject | [PATCH] Remove never-migrates assumption from rcu_process_callbacks() |
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Hello again!
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 <paulmck@linux.vnet.ibm.com> ---
rcupreempt.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff -urpNa -X dontdiff linux-2.6.25-rc3-rcuoffline/kernel/rcupreempt.c linux-2.6.25-rc3-rcuoffline-fp/kernel/rcupreempt.c --- linux-2.6.25-rc3-rcuoffline/kernel/rcupreempt.c 2008-02-26 17:04:17.000000000 -0800 +++ linux-2.6.25-rc3-rcuoffline-fp/kernel/rcupreempt.c 2008-02-27 23:04:18.000000000 -0800 @@ -736,9 +736,11 @@ static void rcu_process_callbacks(struct { 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);
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