diff options
| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2011-10-05 11:45:18 -0700 |
|---|---|---|
| committer | Clark Williams <williams@redhat.com> | 2012-03-13 12:40:12 -0500 |
| commit | 69c34d8d13ef80821ab0341eb497564b7f31dfb5 (patch) | |
| tree | d46f8147385d515f117677da2ba051754be1af1f /kernel/rcutree.h | |
| parent | 5cfc013dbac7eb5ae0d8a4f7c31cb0309de712c9 (diff) | |
rcu: Make ksoftirqd do RCU quiescent states
Implementing RCU-bh in terms of RCU-preempt makes the system vulnerable
to network-based denial-of-service attacks. This patch therefore
makes __do_softirq() invoke rcu_bh_qs(), but only when __do_softirq()
is running in ksoftirqd context. A wrapper layer in interposed so that
other calls to __do_softirq() avoid invoking rcu_bh_qs(). The underlying
function __do_softirq_common() does the actual work.
The reason that rcu_bh_qs() is bad in these non-ksoftirqd contexts is
that there might be a local_bh_enable() inside an RCU-preempt read-side
critical section. This local_bh_enable() can invoke __do_softirq()
directly, so if __do_softirq() were to invoke rcu_bh_qs() (which just
calls rcu_preempt_qs() in the PREEMPT_RT_FULL case), there would be
an illegal RCU-preempt quiescent state in the middle of an RCU-preempt
read-side critical section. Therefore, quiescent states can only happen
in cases where __do_softirq() is invoked directly from ksoftirqd.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20111005184518.GA21601@linux.vnet.ibm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/rcutree.h')
| -rw-r--r-- | kernel/rcutree.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/kernel/rcutree.h b/kernel/rcutree.h index dca495d81304..b5222738c9b0 100644 --- a/kernel/rcutree.h +++ b/kernel/rcutree.h @@ -430,6 +430,7 @@ DECLARE_PER_CPU(char, rcu_cpu_has_work); /* Forward declarations for rcutree_plugin.h */ static void rcu_bootup_announce(void); long rcu_batches_completed(void); +static void rcu_preempt_qs(int cpu); static void rcu_preempt_note_context_switch(int cpu); static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp); #ifdef CONFIG_HOTPLUG_CPU |