diff options
| author | Thomas Gleixner <tglx@linutronix.de> | 2011-10-05 11:59:38 -0700 |
|---|---|---|
| committer | Clark Williams <williams@redhat.com> | 2012-04-13 11:01:42 -0500 |
| commit | d9e16f364c30463714ccb9789dd38bd4057c28fd (patch) | |
| tree | b49d18677035e81dfea8f840c9538af995d334d9 /include/linux/rcupdate.h | |
| parent | 33e7935c81c659618b7f4dc5a98b62f3d3136587 (diff) | |
rcu: Merge RCU-bh into RCU-preempt
The Linux kernel has long RCU-bh read-side critical sections that
intolerably increase scheduling latency under mainline's RCU-bh rules,
which include RCU-bh read-side critical sections being non-preemptible.
This patch therefore arranges for RCU-bh to be implemented in terms of
RCU-preempt for CONFIG_PREEMPT_RT_FULL=y.
This has the downside of defeating the purpose of RCU-bh, namely,
handling the case where the system is subjected to a network-based
denial-of-service attack that keeps at least one CPU doing full-time
softirq processing. This issue will be fixed by a later commit.
The current commit will need some work to make it appropriate for
mainline use, for example, it needs to be extended to cover Tiny RCU.
[ paulmck: Added a useful changelog ]
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20111005185938.GA20403@linux.vnet.ibm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'include/linux/rcupdate.h')
| -rw-r--r-- | include/linux/rcupdate.h | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 23a500f70fcf..888d24ac66ba 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -101,6 +101,9 @@ extern void call_rcu(struct rcu_head *head, #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ +#ifdef CONFIG_PREEMPT_RT_FULL +#define call_rcu_bh call_rcu +#else /** * call_rcu_bh() - Queue an RCU for invocation after a quicker grace period. * @head: structure to be used for queueing the RCU updates. @@ -121,6 +124,7 @@ extern void call_rcu(struct rcu_head *head, */ extern void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *head)); +#endif /** * call_rcu_sched() - Queue an RCU for invocation after sched grace period. @@ -190,7 +194,13 @@ static inline int rcu_preempt_depth(void) /* Internal to kernel */ extern void rcu_sched_qs(int cpu); + +#ifndef CONFIG_PREEMPT_RT_FULL extern void rcu_bh_qs(int cpu); +#else +static inline void rcu_bh_qs(int cpu) { } +#endif + extern void rcu_check_callbacks(int cpu, int user); struct notifier_block; extern void rcu_idle_enter(void); @@ -331,7 +341,14 @@ static inline int rcu_read_lock_held(void) * rcu_read_lock_bh_held() is defined out of line to avoid #include-file * hell. */ +#ifdef CONFIG_PREEMPT_RT_FULL +static inline int rcu_read_lock_bh_held(void) +{ + return rcu_read_lock_held(); +} +#else extern int rcu_read_lock_bh_held(void); +#endif /** * rcu_read_lock_sched_held() - might we be in RCU-sched read-side critical section? @@ -780,10 +797,14 @@ static inline void rcu_read_unlock(void) static inline void rcu_read_lock_bh(void) { local_bh_disable(); +#ifdef CONFIG_PREEMPT_RT_FULL + rcu_read_lock(); +#else __acquire(RCU_BH); rcu_lock_acquire(&rcu_bh_lock_map); rcu_lockdep_assert(!rcu_is_cpu_idle(), "rcu_read_lock_bh() used illegally while idle"); +#endif } /* @@ -793,10 +814,14 @@ static inline void rcu_read_lock_bh(void) */ static inline void rcu_read_unlock_bh(void) { +#ifdef CONFIG_PREEMPT_RT_FULL + rcu_read_unlock(); +#else rcu_lockdep_assert(!rcu_is_cpu_idle(), "rcu_read_unlock_bh() used illegally while idle"); rcu_lock_release(&rcu_bh_lock_map); __release(RCU_BH); +#endif local_bh_enable(); } |