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author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2011-10-05 18:45:18 (GMT) |
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committer | Scott Wood <scottwood@freescale.com> | 2014-05-14 18:38:30 (GMT) |
commit | 9e20ed4e1caedf12d0cafe3542ce95a937cd11da (patch) | |
tree | 624ab4f90f27b6b511c1e61d2239ce845d76966a /kernel/rcutree.c | |
parent | 1bad122a859ae35a5b7cea747121be39d38d6dc8 (diff) | |
download | linux-fsl-qoriq-9e20ed4e1caedf12d0cafe3542ce95a937cd11da.tar.xz |
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.c')
-rw-r--r-- | kernel/rcutree.c | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/kernel/rcutree.c b/kernel/rcutree.c index d52e23b..8104cb2 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -199,7 +199,14 @@ void rcu_sched_qs(int cpu) rdp->passed_quiesce = 1; } -#ifndef CONFIG_PREEMPT_RT_FULL +#ifdef CONFIG_PREEMPT_RT_FULL +static void rcu_preempt_qs(int cpu); + +void rcu_bh_qs(int cpu) +{ + rcu_preempt_qs(cpu); +} +#else void rcu_bh_qs(int cpu) { struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu); |