diff options
author | Thomas Gleixner <tglx@linutronix.de> | 2011-10-05 18:59:38 (GMT) |
---|---|---|
committer | Scott Wood <scottwood@freescale.com> | 2015-02-13 22:20:48 (GMT) |
commit | 87d06a43902d0ffa6e10e88da44909fe5082da43 (patch) | |
tree | f45081bea3972290f51f542cc87d60c69294fcdf | |
parent | c8fca640b57490daf79b014ffa54d737ee85f88e (diff) | |
download | linux-fsl-qoriq-87d06a43902d0ffa6e10e88da44909fe5082da43.tar.xz |
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>
-rw-r--r-- | include/linux/rcupdate.h | 25 | ||||
-rw-r--r-- | include/linux/rcutree.h | 18 | ||||
-rw-r--r-- | kernel/rcupdate.c | 2 | ||||
-rw-r--r-- | kernel/rcutree.c | 10 |
4 files changed, 53 insertions, 2 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index e56a6b2..7d754bf 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -128,6 +128,9 @@ 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. @@ -151,6 +154,7 @@ 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. @@ -225,7 +229,13 @@ static inline int rcu_preempt_depth(void) /* Internal to kernel */ extern void rcu_init(void); extern void rcu_sched_qs(int cpu); + +#ifdef CONFIG_PREEMPT_RT_FULL +static inline void rcu_bh_qs(int cpu) { } +#else extern 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); @@ -369,7 +379,14 @@ 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? @@ -826,10 +843,14 @@ 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 } /* @@ -839,10 +860,14 @@ 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(); } diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index 226169d..91333de 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -44,7 +44,11 @@ static inline void rcu_virt_note_context_switch(int cpu) rcu_note_context_switch(cpu); } +#ifdef CONFIG_PREEMPT_RT_FULL +# define synchronize_rcu_bh synchronize_rcu +#else extern void synchronize_rcu_bh(void); +#endif extern void synchronize_sched_expedited(void); extern void synchronize_rcu_expedited(void); @@ -72,17 +76,19 @@ static inline void synchronize_rcu_bh_expedited(void) } extern void rcu_barrier(void); +#ifdef CONFIG_PREEMPT_RT_FULL +# define rcu_barrier_bh rcu_barrier +#else extern void rcu_barrier_bh(void); +#endif extern void rcu_barrier_sched(void); extern unsigned long rcutorture_testseq; extern unsigned long rcutorture_vernum; extern long rcu_batches_completed(void); -extern long rcu_batches_completed_bh(void); extern long rcu_batches_completed_sched(void); extern void rcu_force_quiescent_state(void); -extern void rcu_bh_force_quiescent_state(void); extern void rcu_sched_force_quiescent_state(void); extern void exit_rcu(void); @@ -90,4 +96,12 @@ extern void exit_rcu(void); extern void rcu_scheduler_starting(void); extern int rcu_scheduler_active __read_mostly; +#ifndef CONFIG_PREEMPT_RT_FULL +extern void rcu_bh_force_quiescent_state(void); +extern long rcu_batches_completed_bh(void); +#else +# define rcu_bh_force_quiescent_state rcu_force_quiescent_state +# define rcu_batches_completed_bh rcu_batches_completed +#endif + #endif /* __LINUX_RCUTREE_H */ diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c index b02a339..7e1dd3e 100644 --- a/kernel/rcupdate.c +++ b/kernel/rcupdate.c @@ -129,6 +129,7 @@ int notrace debug_lockdep_rcu_enabled(void) } EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled); +#ifndef CONFIG_PREEMPT_RT_FULL /** * rcu_read_lock_bh_held() - might we be in RCU-bh read-side critical section? * @@ -155,6 +156,7 @@ int rcu_read_lock_bh_held(void) return in_softirq() || irqs_disabled(); } EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held); +#endif #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 610b887..5521a4b 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -199,6 +199,7 @@ void rcu_sched_qs(int cpu) rdp->passed_quiesce = 1; } +#ifndef CONFIG_PREEMPT_RT_FULL void rcu_bh_qs(int cpu) { struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu); @@ -207,6 +208,7 @@ void rcu_bh_qs(int cpu) trace_rcu_grace_period(TPS("rcu_bh"), rdp->gpnum, TPS("cpuqs")); rdp->passed_quiesce = 1; } +#endif /* * Note a context switch. This is a quiescent state for RCU-sched, @@ -263,6 +265,7 @@ long rcu_batches_completed_sched(void) } EXPORT_SYMBOL_GPL(rcu_batches_completed_sched); +#ifndef CONFIG_PREEMPT_RT_FULL /* * Return the number of RCU BH batches processed thus far for debug & stats. */ @@ -280,6 +283,7 @@ void rcu_bh_force_quiescent_state(void) force_quiescent_state(&rcu_bh_state); } EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state); +#endif /* * Record the number of times rcutorture tests have been initiated and @@ -2389,6 +2393,7 @@ void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) } EXPORT_SYMBOL_GPL(call_rcu_sched); +#ifndef CONFIG_PREEMPT_RT_FULL /* * Queue an RCU callback for invocation after a quicker grace period. */ @@ -2397,6 +2402,7 @@ void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) __call_rcu(head, func, &rcu_bh_state, -1, 0); } EXPORT_SYMBOL_GPL(call_rcu_bh); +#endif /* * Because a context switch is a grace period for RCU-sched and RCU-bh, @@ -2474,6 +2480,7 @@ void synchronize_sched(void) } EXPORT_SYMBOL_GPL(synchronize_sched); +#ifndef CONFIG_PREEMPT_RT_FULL /** * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed. * @@ -2500,6 +2507,7 @@ void synchronize_rcu_bh(void) wait_rcu_gp(call_rcu_bh); } EXPORT_SYMBOL_GPL(synchronize_rcu_bh); +#endif static int synchronize_sched_expedited_cpu_stop(void *data) { @@ -2911,6 +2919,7 @@ static void _rcu_barrier(struct rcu_state *rsp) mutex_unlock(&rsp->barrier_mutex); } +#ifndef CONFIG_PREEMPT_RT_FULL /** * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete. */ @@ -2919,6 +2928,7 @@ void rcu_barrier_bh(void) _rcu_barrier(&rcu_bh_state); } EXPORT_SYMBOL_GPL(rcu_barrier_bh); +#endif /** * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks. |