From 2a1d446019f9a5983ec5a335b95e8593fdb6fa2e Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Mon, 16 Jul 2012 10:42:36 +0000 Subject: kthread: Implement park/unpark facility To avoid the full teardown/setup of per cpu kthreads in the case of cpu hot(un)plug, provide a facility which allows to put the kthread into a park position and unpark it when the cpu comes online again. Signed-off-by: Thomas Gleixner Reviewed-by: Namhyung Kim Cc: Peter Zijlstra Reviewed-by: Srivatsa S. Bhat Cc: Rusty Russell Reviewed-by: Paul E. McKenney Link: http://lkml.kernel.org/r/20120716103948.236618824@linutronix.de Signed-off-by: Thomas Gleixner --- include/linux/kthread.h | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) (limited to 'include') diff --git a/include/linux/kthread.h b/include/linux/kthread.h index 22ccf9dee177..8d816646f766 100644 --- a/include/linux/kthread.h +++ b/include/linux/kthread.h @@ -14,6 +14,11 @@ struct task_struct *kthread_create_on_node(int (*threadfn)(void *data), kthread_create_on_node(threadfn, data, -1, namefmt, ##arg) +struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data), + void *data, + unsigned int cpu, + const char *namefmt); + /** * kthread_run - create and wake a thread. * @threadfn: the function to run until signal_pending(current). @@ -34,9 +39,13 @@ struct task_struct *kthread_create_on_node(int (*threadfn)(void *data), void kthread_bind(struct task_struct *k, unsigned int cpu); int kthread_stop(struct task_struct *k); -int kthread_should_stop(void); +bool kthread_should_stop(void); +bool kthread_should_park(void); bool kthread_freezable_should_stop(bool *was_frozen); void *kthread_data(struct task_struct *k); +int kthread_park(struct task_struct *k); +void kthread_unpark(struct task_struct *k); +void kthread_parkme(void); int kthreadd(void *unused); extern struct task_struct *kthreadd_task; -- cgit v1.2.3 From f97f8f06a49febbc3cb3635172efbe64ddc79700 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Mon, 16 Jul 2012 10:42:36 +0000 Subject: smpboot: Provide infrastructure for percpu hotplug threads Provide a generic interface for setting up and tearing down percpu threads. On registration the threads for already online cpus are created and started. On deregistration (modules) the threads are stoppped. During hotplug operations the threads are created, started, parked and unparked. The datastructure for registration provides a pointer to percpu storage space and optional setup, cleanup, park, unpark functions. These functions are called when the thread state changes. Each implementation has to provide a function which is queried and returns whether the thread should run and the thread function itself. The core code handles all state transitions and avoids duplicated code in the call sites. [ paulmck: Preemption leak fix ] Signed-off-by: Thomas Gleixner Cc: Peter Zijlstra Reviewed-by: Srivatsa S. Bhat Cc: Rusty Russell Reviewed-by: Paul E. McKenney Cc: Namhyung Kim Link: http://lkml.kernel.org/r/20120716103948.352501068@linutronix.de Signed-off-by: Thomas Gleixner --- include/linux/smpboot.h | 43 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 43 insertions(+) create mode 100644 include/linux/smpboot.h (limited to 'include') diff --git a/include/linux/smpboot.h b/include/linux/smpboot.h new file mode 100644 index 000000000000..e0106d8581d3 --- /dev/null +++ b/include/linux/smpboot.h @@ -0,0 +1,43 @@ +#ifndef _LINUX_SMPBOOT_H +#define _LINUX_SMPBOOT_H + +#include + +struct task_struct; +/* Cookie handed to the thread_fn*/ +struct smpboot_thread_data; + +/** + * struct smp_hotplug_thread - CPU hotplug related thread descriptor + * @store: Pointer to per cpu storage for the task pointers + * @list: List head for core management + * @thread_should_run: Check whether the thread should run or not. Called with + * preemption disabled. + * @thread_fn: The associated thread function + * @setup: Optional setup function, called when the thread gets + * operational the first time + * @cleanup: Optional cleanup function, called when the thread + * should stop (module exit) + * @park: Optional park function, called when the thread is + * parked (cpu offline) + * @unpark: Optional unpark function, called when the thread is + * unparked (cpu online) + * @thread_comm: The base name of the thread + */ +struct smp_hotplug_thread { + struct task_struct __percpu **store; + struct list_head list; + int (*thread_should_run)(unsigned int cpu); + void (*thread_fn)(unsigned int cpu); + void (*setup)(unsigned int cpu); + void (*cleanup)(unsigned int cpu, bool online); + void (*park)(unsigned int cpu); + void (*unpark)(unsigned int cpu); + const char *thread_comm; +}; + +int smpboot_register_percpu_thread(struct smp_hotplug_thread *plug_thread); +void smpboot_unregister_percpu_thread(struct smp_hotplug_thread *plug_thread); +int smpboot_thread_schedule(void); + +#endif -- cgit v1.2.3 From 7ece55a4a3a04abe37118b1d4fb0b702eeb1de4c Mon Sep 17 00:00:00 2001 From: Josh Triplett Date: Tue, 4 Sep 2012 23:23:06 -0700 Subject: trace: Don't declare trace_*_rcuidle functions in modules Tracepoints declare a static inline trace_*_rcuidle variant of the trace function, to support safely generating trace events from the idle loop. Module code never actually uses that variant of trace functions, because modules don't run code that needs tracing with RCU idled. However, the declaration of those otherwise unused functions causes the module to reference rcu_idle_exit and rcu_idle_enter, which RCU does not export to modules. To avoid this, don't generate trace_*_rcuidle functions for tracepoints declared in module code. Link: http://lkml.kernel.org/r/20120905062306.GA14756@leaf Reported-by: Steven Rostedt Acked-by: Mathieu Desnoyers Acked-by: Paul E. McKenney Signed-off-by: Josh Triplett Signed-off-by: Steven Rostedt --- include/linux/tracepoint.h | 28 ++++++++++++++++++---------- 1 file changed, 18 insertions(+), 10 deletions(-) (limited to 'include') diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h index 802de56c41e8..2f322c38bd4d 100644 --- a/include/linux/tracepoint.h +++ b/include/linux/tracepoint.h @@ -136,6 +136,22 @@ static inline void tracepoint_synchronize_unregister(void) postrcu; \ } while (0) +#ifndef MODULE +#define __DECLARE_TRACE_RCU(name, proto, args, cond, data_proto, data_args) \ + static inline void trace_##name##_rcuidle(proto) \ + { \ + if (static_key_false(&__tracepoint_##name.key)) \ + __DO_TRACE(&__tracepoint_##name, \ + TP_PROTO(data_proto), \ + TP_ARGS(data_args), \ + TP_CONDITION(cond), \ + rcu_idle_exit(), \ + rcu_idle_enter()); \ + } +#else +#define __DECLARE_TRACE_RCU(name, proto, args, cond, data_proto, data_args) +#endif + /* * Make sure the alignment of the structure in the __tracepoints section will * not add unwanted padding between the beginning of the section and the @@ -151,16 +167,8 @@ static inline void tracepoint_synchronize_unregister(void) TP_ARGS(data_args), \ TP_CONDITION(cond),,); \ } \ - static inline void trace_##name##_rcuidle(proto) \ - { \ - if (static_key_false(&__tracepoint_##name.key)) \ - __DO_TRACE(&__tracepoint_##name, \ - TP_PROTO(data_proto), \ - TP_ARGS(data_args), \ - TP_CONDITION(cond), \ - rcu_idle_exit(), \ - rcu_idle_enter()); \ - } \ + __DECLARE_TRACE_RCU(name, PARAMS(proto), PARAMS(args), \ + PARAMS(cond), PARAMS(data_proto), PARAMS(data_args)) \ static inline int \ register_trace_##name(void (*probe)(data_proto), void *data) \ { \ -- cgit v1.2.3 From b4270ee356e5ecef5394ab80c0a0301c1676b7f0 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 31 Jul 2012 10:12:48 -0700 Subject: rcu: Permit RCU_NONIDLE() to be used from interrupt context There is a need to use RCU from interrupt context, but either before rcu_irq_enter() is called or after rcu_irq_exit() is called. If the interrupt occurs from idle, then lockdep-RCU will complain about such uses, as they appear to be illegal uses of RCU from the idle loop. In other environments, RCU_NONIDLE() could be used to properly protect the use of RCU, but RCU_NONIDLE() currently cannot be invoked except from process context. This commit therefore modifies RCU_NONIDLE() to permit its use more globally. Reported-by: Steven Rostedt Signed-off-by: Paul E. McKenney Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) (limited to 'include') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 115ead2b5155..0fbbd52e01f9 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -210,14 +210,12 @@ extern void exit_rcu(void); * to nest RCU_NONIDLE() wrappers, but the nesting level is currently * quite limited. If deeper nesting is required, it will be necessary * to adjust DYNTICK_TASK_NESTING_VALUE accordingly. - * - * This macro may be used from process-level code only. */ #define RCU_NONIDLE(a) \ do { \ - rcu_idle_exit(); \ + rcu_irq_enter(); \ do { a; } while (0); \ - rcu_idle_enter(); \ + rcu_irq_exit(); \ } while (0) /* -- cgit v1.2.3 From 803b0ebae921714d1c36f0996db8125eda5fae53 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 23 Aug 2012 08:34:07 -0700 Subject: time: RCU permitted to stop idle entry via softirq The can_stop_idle_tick() function complains if a softirq vector is raised too late in the idle-entry process, presumably in order to prevent dangling softirq invocations from being delayed across the full idle period, which might be indefinitely long -- and if softirq was asserted any later than the call to this function, such a delay might well happen. However, RCU needs to be able to use softirq to stop idle entry in order to be able to drain RCU callbacks from the current CPU, which in turn enables faster entry into dyntick-idle mode, which in turn reduces power consumption. Because RCU takes this action at a well-defined point in the idle-entry path, it is safe for RCU to take this approach. This commit therefore silences the error message that is sometimes produced when the going-idle CPU suddenly finds that it has an RCU_SOFTIRQ to process. The error message will continue to be issued for other softirq vectors. Reported-by: Sedat Dilek Signed-off-by: Paul E. McKenney Signed-off-by: Paul E. McKenney Tested-by: Sedat Dilek Reviewed-by: Josh Triplett --- include/linux/interrupt.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include') diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h index c5f856a040b9..5e4e6170f43a 100644 --- a/include/linux/interrupt.h +++ b/include/linux/interrupt.h @@ -430,6 +430,8 @@ enum NR_SOFTIRQS }; +#define SOFTIRQ_STOP_IDLE_MASK (~(1 << RCU_SOFTIRQ)) + /* map softirq index to softirq name. update 'softirq_to_name' in * kernel/softirq.c when adding a new softirq. */ -- cgit v1.2.3 From adf5091e6ccaa02905e7a28f9ff44f46c7f4c230 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Thu, 28 Jun 2012 11:20:21 -0700 Subject: rcu: New rcu_user_enter() and rcu_user_exit() APIs RCU currently insists that only idle tasks can enter RCU idle mode, which prohibits an adaptive tickless kernel (AKA nohz cpusets), which in turn would mean that usermode execution would always take scheduling-clock interrupts, even when there is only one task runnable on the CPU in question. This commit therefore adds rcu_user_enter() and rcu_user_exit(), which allow non-idle tasks to enter RCU idle mode. These are quite similar to rcu_idle_enter() and rcu_idle_exit(), respectively, except that they omit the idle-task checks. [ Updated to use "user" flag rather than separate check functions. ] [ paulmck: Updated to drop exports of new functions based on Josh's patch getting rid of the need for them. ] Signed-off-by: Frederic Weisbecker Signed-off-by: Paul E. McKenney Cc: Alessio Igor Bogani Cc: Andrew Morton Cc: Avi Kivity Cc: Chris Metcalf Cc: Christoph Lameter Cc: Daniel Lezcano Cc: Geoff Levand Cc: Gilad Ben Yossef Cc: Hakan Akkan Cc: Ingo Molnar Cc: Kevin Hilman Cc: Max Krasnyansky Cc: Peter Zijlstra Cc: Stephen Hemminger Cc: Steven Rostedt Cc: Sven-Thorsten Dietrich Cc: Thomas Gleixner Reviewed-by: Josh Triplett --- include/linux/rcupdate.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 0fbbd52e01f9..d8b20bfd4795 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -191,6 +191,8 @@ extern void rcu_idle_enter(void); extern void rcu_idle_exit(void); extern void rcu_irq_enter(void); extern void rcu_irq_exit(void); +extern void rcu_user_enter(void); +extern void rcu_user_exit(void); extern void exit_rcu(void); /** -- cgit v1.2.3 From 19dd1591fc379f1d89f39cd99cbbe97433baa3c3 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Mon, 4 Jun 2012 16:42:35 -0700 Subject: rcu: New rcu_user_enter_after_irq() and rcu_user_exit_after_irq() APIs In some cases, it is necessary to enter or exit userspace-RCU-idle mode from an interrupt handler, for example, if some other CPU sends this CPU a resched IPI. In this case, the current CPU would enter the IPI handler in userspace-RCU-idle mode, but would need to exit the IPI handler after having exited that mode. To allow this to work, this commit adds two new APIs to TREE_RCU: - rcu_user_enter_after_irq(). This must be called from an interrupt between rcu_irq_enter() and rcu_irq_exit(). After the irq calls rcu_irq_exit(), the irq handler will return into an RCU extended quiescent state. In theory, this interrupt is never a nested interrupt, but in practice it might interrupt softirq, which looks to RCU like a nested interrupt. - rcu_user_exit_after_irq(). This must be called from a non-nesting interrupt, interrupting an RCU extended quiescent state, also between rcu_irq_enter() and rcu_irq_exit(). After the irq calls rcu_irq_exit(), the irq handler will return in an RCU non-quiescent state. [ Combined with "Allow calls to rcu_exit_user_irq from nesting irqs." ] Signed-off-by: Frederic Weisbecker Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett --- include/linux/rcupdate.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index d8b20bfd4795..f818dd165b44 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -193,6 +193,8 @@ extern void rcu_irq_enter(void); extern void rcu_irq_exit(void); extern void rcu_user_enter(void); extern void rcu_user_exit(void); +extern void rcu_user_enter_after_irq(void); +extern void rcu_user_exit_after_irq(void); extern void exit_rcu(void); /** -- cgit v1.2.3 From 2b1d5024e17be459aa6385763ca3faa8f01c52d9 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Wed, 11 Jul 2012 20:26:30 +0200 Subject: rcu: Settle config for userspace extended quiescent state Create a new config option under the RCU menu that put CPUs under RCU extended quiescent state (as in dynticks idle mode) when they run in userspace. This require some contribution from architectures to hook into kernel and userspace boundaries. Signed-off-by: Frederic Weisbecker Cc: Alessio Igor Bogani Cc: Andrew Morton Cc: Avi Kivity Cc: Chris Metcalf Cc: Christoph Lameter Cc: Geoff Levand Cc: Gilad Ben Yossef Cc: Hakan Akkan Cc: H. Peter Anvin Cc: Ingo Molnar Cc: Josh Triplett Cc: Kevin Hilman Cc: Max Krasnyansky Cc: Peter Zijlstra Cc: Stephen Hemminger Cc: Steven Rostedt Cc: Sven-Thorsten Dietrich Cc: Thomas Gleixner Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett --- include/linux/rcupdate.h | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'include') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index f818dd165b44..f5034f22e94b 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -191,10 +191,19 @@ extern void rcu_idle_enter(void); extern void rcu_idle_exit(void); extern void rcu_irq_enter(void); extern void rcu_irq_exit(void); + +#ifdef CONFIG_RCU_USER_QS extern void rcu_user_enter(void); extern void rcu_user_exit(void); extern void rcu_user_enter_after_irq(void); extern void rcu_user_exit_after_irq(void); +#else +static inline void rcu_user_enter(void) { } +static inline void rcu_user_exit(void) { } +static inline void rcu_user_enter_after_irq(void) { } +static inline void rcu_user_exit_after_irq(void) { } +#endif /* CONFIG_RCU_USER_QS */ + extern void exit_rcu(void); /** -- cgit v1.2.3 From 04e7e951532b390b16feb070be9972b8fad2fc57 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Mon, 16 Jul 2012 15:06:40 -0700 Subject: rcu: Switch task's syscall hooks on context switch Clear the syscalls hook of a task when it's scheduled out so that if the task migrates, it doesn't run the syscall slow path on a CPU that might not need it. Also set the syscalls hook on the next task if needed. Signed-off-by: Frederic Weisbecker Cc: Alessio Igor Bogani Cc: Andrew Morton Cc: Avi Kivity Cc: Chris Metcalf Cc: Christoph Lameter Cc: Geoff Levand Cc: Gilad Ben Yossef Cc: Hakan Akkan Cc: H. Peter Anvin Cc: Ingo Molnar Cc: Josh Triplett Cc: Kevin Hilman Cc: Max Krasnyansky Cc: Peter Zijlstra Cc: Stephen Hemminger Cc: Steven Rostedt Cc: Sven-Thorsten Dietrich Cc: Thomas Gleixner Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett --- include/linux/rcupdate.h | 2 ++ include/linux/sched.h | 8 ++++++++ 2 files changed, 10 insertions(+) (limited to 'include') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index f5034f22e94b..7c968e4f929e 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -197,6 +197,8 @@ extern void rcu_user_enter(void); extern void rcu_user_exit(void); extern void rcu_user_enter_after_irq(void); extern void rcu_user_exit_after_irq(void); +extern void rcu_user_hooks_switch(struct task_struct *prev, + struct task_struct *next); #else static inline void rcu_user_enter(void) { } static inline void rcu_user_exit(void) { } diff --git a/include/linux/sched.h b/include/linux/sched.h index 23bddac4bad8..335720a1fc33 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1885,6 +1885,14 @@ static inline void rcu_copy_process(struct task_struct *p) #endif +static inline void rcu_switch(struct task_struct *prev, + struct task_struct *next) +{ +#ifdef CONFIG_RCU_USER_QS + rcu_user_hooks_switch(prev, next); +#endif +} + static inline void tsk_restore_flags(struct task_struct *task, unsigned long orig_flags, unsigned long flags) { -- cgit v1.2.3