summaryrefslogtreecommitdiff
path: root/kernel/rcuclassic.c
diff options
context:
space:
mode:
authorLinus Torvalds <torvalds@linux-foundation.org>2008-07-02 18:59:45 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2008-07-02 18:59:45 -0700
commitc000131c711f68cb68712e6553ddce5fa6ad5c5c (patch)
treebfb29b294e7e01d74f7f9a4ef040d27b0b936ced /kernel/rcuclassic.c
parent041924ec2f40efa6a3163144a5481a000804199d (diff)
parent8558f8f81680a43d383abd1b5f23d3501fedfa65 (diff)
downloadconfigs-c000131c711f68cb68712e6553ddce5fa6ad5c5c.tar.gz
Merge branch 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: rcu: fix hotplug vs rcu race
Diffstat (limited to 'kernel/rcuclassic.c')
-rw-r--r--kernel/rcuclassic.c16
1 files changed, 15 insertions, 1 deletions
diff --git a/kernel/rcuclassic.c b/kernel/rcuclassic.c
index f4ffbd0f306..a38895a5b8e 100644
--- a/kernel/rcuclassic.c
+++ b/kernel/rcuclassic.c
@@ -89,8 +89,22 @@ static void force_quiescent_state(struct rcu_data *rdp,
/*
* Don't send IPI to itself. With irqs disabled,
* rdp->cpu is the current cpu.
+ *
+ * cpu_online_map is updated by the _cpu_down()
+ * using stop_machine_run(). Since we're in irqs disabled
+ * section, stop_machine_run() is not exectuting, hence
+ * the cpu_online_map is stable.
+ *
+ * However, a cpu might have been offlined _just_ before
+ * we disabled irqs while entering here.
+ * And rcu subsystem might not yet have handled the CPU_DEAD
+ * notification, leading to the offlined cpu's bit
+ * being set in the rcp->cpumask.
+ *
+ * Hence cpumask = (rcp->cpumask & cpu_online_map) to prevent
+ * sending smp_reschedule() to an offlined CPU.
*/
- cpumask = rcp->cpumask;
+ cpus_and(cpumask, rcp->cpumask, cpu_online_map);
cpu_clear(rdp->cpu, cpumask);
for_each_cpu_mask(cpu, cpumask)
smp_send_reschedule(cpu);