diff options
author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2011-10-05 11:45:18 -0700 |
---|---|---|
committer | Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2016-02-13 00:36:09 +0100 |
commit | 842b1983f15a70ce956190d29e69caa35bd88e62 (patch) | |
tree | 6686f2242fdb1406901bcc655ccb5bddef597b98 | |
parent | 94cc0f6ff449f4a87f675a6bb60c263b0a6c5aac (diff) | |
download | rt-linux-842b1983f15a70ce956190d29e69caa35bd88e62.tar.gz |
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>
-rw-r--r-- | include/linux/rcupdate.h | 4 | ||||
-rw-r--r-- | kernel/rcu/tree.c | 9 | ||||
-rw-r--r-- | kernel/rcu/tree_plugin.h | 8 |
3 files changed, 15 insertions, 6 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index ddacc7e629111..c2f5f955163d7 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -334,11 +334,7 @@ static inline int rcu_preempt_depth(void) void rcu_init(void); void rcu_end_inkernel_boot(void); void rcu_sched_qs(void); -#ifdef CONFIG_PREEMPT_RT_FULL -static inline void rcu_bh_qs(void) { } -#else void rcu_bh_qs(void); -#endif void rcu_check_callbacks(int user); struct notifier_block; int rcu_cpu_notify(struct notifier_block *self, diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index d52db2c442e3e..eadbeb631f55d 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -266,7 +266,14 @@ void rcu_sched_qs(void) } } -#ifndef CONFIG_PREEMPT_RT_FULL +#ifdef CONFIG_PREEMPT_RT_FULL +static void rcu_preempt_qs(void); + +void rcu_bh_qs(void) +{ + rcu_preempt_qs(); +} +#else void rcu_bh_qs(void) { if (__this_cpu_read(rcu_bh_data.cpu_no_qs.s)) { diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index ccac43b7170c8..13ce51b08de0b 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -28,6 +28,7 @@ #include <linux/gfp.h> #include <linux/oom.h> #include <linux/smpboot.h> +#include <linux/jiffies.h> #include "../time/tick-internal.h" #ifdef CONFIG_RCU_BOOST @@ -1346,7 +1347,7 @@ static void rcu_prepare_kthreads(int cpu) #endif /* #else #ifdef CONFIG_RCU_BOOST */ -#if !defined(CONFIG_RCU_FAST_NO_HZ) +#if !defined(CONFIG_RCU_FAST_NO_HZ) || defined(CONFIG_PREEMPT_RT_FULL) /* * Check to see if any future RCU-related work will need to be done @@ -1363,7 +1364,9 @@ int rcu_needs_cpu(u64 basemono, u64 *nextevt) return IS_ENABLED(CONFIG_RCU_NOCB_CPU_ALL) ? 0 : rcu_cpu_has_callbacks(NULL); } +#endif /* !defined(CONFIG_RCU_FAST_NO_HZ) || defined(CONFIG_PREEMPT_RT_FULL) */ +#if !defined(CONFIG_RCU_FAST_NO_HZ) /* * Because we do not have RCU_FAST_NO_HZ, don't bother cleaning up * after it. @@ -1459,6 +1462,8 @@ static bool __maybe_unused rcu_try_advance_all_cbs(void) return cbs_ready; } +#ifndef CONFIG_PREEMPT_RT_FULL + /* * Allow the CPU to enter dyntick-idle mode unless it has callbacks ready * to invoke. If the CPU has callbacks, try to advance them. Tell the @@ -1504,6 +1509,7 @@ int rcu_needs_cpu(u64 basemono, u64 *nextevt) *nextevt = basemono + dj * TICK_NSEC; return 0; } +#endif /* #ifndef CONFIG_PREEMPT_RT_FULL */ /* * Prepare a CPU for idle from an RCU perspective. The first major task |