litmus-rt.git - The LITMUS^RT kernel.

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author	Michael wang <wangyun@linux.vnet.ibm.com>	2013-11-12 22:10:56 -0500
committer	Ingo Molnar <mingo@kernel.org>	2013-11-13 07:33:50 -0500
commit	106dd5afde3cd10db7e1370b6ddc77f0b2496a75 (patch)
tree	5a83870657588c076e17d59a19a3c27f20fe38cb /tools/perf/scripts/python/sched-migration.py
parent	9b66bfb28049594fe2bb2b91607ba302f511ce8b (diff)

sched: Fix endless sync_sched/rcu() loop inside _cpu_down()

Commit 6acce3ef8: sched: Remove get_online_cpus() usage tries to do sync_sched/rcu() inside _cpu_down() but triggers: INFO: task swapper/0:1 blocked for more than 120 seconds. ... [<ffffffff811263dc>] synchronize_rcu+0x2c/0x30 [<ffffffff81d1bd82>] _cpu_down+0x2b2/0x340 ... It was caused by that in the rcu boost case we rely on smpboot thread to finish the rcu callback, which has already been parked before sync in here and leads to the endless sync_sched/rcu(). This patch exchanges the sequence of smpboot_park_threads() and sync_sched/rcu() to fix the bug. Reported-by: Fengguang Wu <fengguang.wu@intel.com> Tested-by: Fengguang Wu <fengguang.wu@intel.com> Signed-off-by: Michael Wang <wangyun@linux.vnet.ibm.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/5282EDC0.6060003@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>

Diffstat (limited to 'tools/perf/scripts/python/sched-migration.py')

0 files changed, 0 insertions, 0 deletions

/* * Read-Copy Update mechanism for mutual exclusion * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. * * Copyright IBM Corporation, 2001 * * Author: Dipankar Sarma <dipankar@in.ibm.com> * * Based on the original work by Paul McKenney <paulmck@us.ibm.com> * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. * Papers: * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001) * * For detailed explanation of Read-Copy Update mechanism see - * http://lse.sourceforge.net/locking/rcupdate.html * */ #ifndef __LINUX_RCUPDATE_H #define __LINUX_RCUPDATE_H #include <linux/types.h> #include <linux/cache.h> #include <linux/spinlock.h> #include <linux/threads.h> #include <linux/cpumask.h> #include <linux/seqlock.h> #include <linux/lockdep.h> #include <linux/completion.h> #include <linux/debugobjects.h> #include <linux/bug.h> #include <linux/compiler.h> #ifdef CONFIG_RCU_TORTURE_TEST extern int rcutorture_runnable; /* for sysctl */ #endif /* #ifdef CONFIG_RCU_TORTURE_TEST */ #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) extern void rcutorture_record_test_transition(void); extern void rcutorture_record_progress(unsigned long vernum); extern void do_trace_rcu_torture_read(const char *rcutorturename, struct rcu_head *rhp, unsigned long secs, unsigned long c_old, unsigned long c); #else static inline void rcutorture_record_test_transition(void) { } static inline void rcutorture_record_progress(unsigned long vernum) { } #ifdef CONFIG_RCU_TRACE extern void do_trace_rcu_torture_read(const char *rcutorturename, struct rcu_head *rhp, unsigned long secs, unsigned long c_old, unsigned long c); #else #define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \ do { } while (0) #endif #endif #define UINT_CMP_GE(a, b) (UINT_MAX / 2 >= (a) - (b)) #define UINT_CMP_LT(a, b) (UINT_MAX / 2 < (a) - (b)) #define ULONG_CMP_GE(a, b) (ULONG_MAX / 2 >= (a) - (b)) #define ULONG_CMP_LT(a, b) (ULONG_MAX / 2 < (a) - (b)) #define ulong2long(a) (*(long *)(&(a))) /* Exported common interfaces */ #ifdef CONFIG_PREEMPT_RCU /** * call_rcu() - Queue an RCU callback for invocation after a grace period. * @head: structure to be used for queueing the RCU updates. * @func: actual callback function to be invoked after the grace period * * The callback function will be invoked some time after a full grace * period elapses, in other words after all pre-existing RCU read-side * critical sections have completed. However, the callback function * might well execute concurrently with RCU read-side critical sections * that started after call_rcu() was invoked. RCU read-side critical * sections are delimited by rcu_read_lock() and rcu_read_unlock(), * and may be nested. * * Note that all CPUs must agree that the grace period extended beyond * all pre-existing RCU read-side critical section. On systems with more * than one CPU, this means that when "func()" is invoked, each CPU is * guaranteed to have executed a full memory barrier since the end of its * last RCU read-side critical section whose beginning preceded the call * to call_rcu(). It also means that each CPU executing an RCU read-side * critical section that continues beyond the start of "func()" must have * executed a memory barrier after the call_rcu() but before the beginning * of that RCU read-side critical section. Note that these guarantees * include CPUs that are offline, idle, or executing in user mode, as * well as CPUs that are executing in the kernel. * * Furthermore, if CPU A invoked call_rcu() and CPU B invoked the * resulting RCU callback function "func()", then both CPU A and CPU B are * guaranteed to execute a full memory barrier during the time interval * between the call to call_rcu() and the invocation of "func()" -- even * if CPU A and CPU B are the same CPU (but again only if the system has * more than one CPU). */ extern void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *head)); #else /* #ifdef CONFIG_PREEMPT_RCU */ /* In classic RCU, call_rcu() is just call_rcu_sched(). */ #define call_rcu call_rcu_sched #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ /** * call_rcu_bh() - Queue an RCU for invocation after a quicker grace period. * @head: structure to be used for queueing the RCU updates. * @func: actual callback function to be invoked after the grace period * * The callback function will be invoked some time after a full grace * period elapses, in other words after all currently executing RCU * read-side critical sections have completed. call_rcu_bh() assumes * that the read-side critical sections end on completion of a softirq * handler. This means that read-side critical sections in process * context must not be interrupted by softirqs. This interface is to be * used when most of the read-side critical sections are in softirq context. * RCU read-side critical sections are delimited by : * - rcu_read_lock() and rcu_read_unlock(), if in interrupt context. * OR * - rcu_read_lock_bh() and rcu_read_unlock_bh(), if in process context. * These may be nested. * * See the description of call_rcu() for more detailed information on * memory ordering guarantees. */ extern void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *head)); /** * call_rcu_sched() - Queue an RCU for invocation after sched grace period. * @head: structure to be used for queueing the RCU updates. * @func: actual callback function to be invoked after the grace period * * The callback function will be invoked some time after a full grace * period elapses, in other words after all currently executing RCU * read-side critical sections have completed. call_rcu_sched() assumes * that the read-side critical sections end on enabling of preemption * or on voluntary preemption. * RCU read-side critical sections are delimited by : * - rcu_read_lock_sched() and rcu_read_unlock_sched(), * OR * anything that disables preemption. * These may be nested. * * See the description of call_rcu() for more detailed information on * memory ordering guarantees. */ extern void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)); extern void synchronize_sched(void); #ifdef CONFIG_PREEMPT_RCU extern void __rcu_read_lock(void); extern void __rcu_read_unlock(void); extern void rcu_read_unlock_special(struct task_struct *t); void synchronize_rcu(void); /* * Defined as a macro as it is a very low level header included from * areas that don't even know about current. This gives the rcu_read_lock() * nesting depth, but makes sense only if CONFIG_PREEMPT_RCU -- in other * types of kernel builds, the rcu_read_lock() nesting depth is unknowable. */ #define rcu_preempt_depth() (current->rcu_read_lock_nesting) #else /* #ifdef CONFIG_PREEMPT_RCU */ static inline void __rcu_read_lock(void) { preempt_disable(); } static inline void __rcu_read_unlock(void) { preempt_enable(); } static inline void synchronize_rcu(void) { synchronize_sched(); } static inline int rcu_preempt_depth(void) { return 0; } #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ /* Internal to kernel */ extern void rcu_init(void); extern void rcu_sched_qs(int cpu); extern void rcu_bh_qs(int cpu); extern void rcu_check_callbacks(int cpu, int user); struct notifier_block; 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); #else static inline void rcu_user_enter(void) { } static inline void rcu_user_exit(void) { } static inline void rcu_user_hooks_switch(struct task_struct *prev, struct task_struct *next) { } #endif /* CONFIG_RCU_USER_QS */ /** * RCU_NONIDLE - Indicate idle-loop code that needs RCU readers * @a: Code that RCU needs to pay attention to. * * RCU, RCU-bh, and RCU-sched read-side critical sections are forbidden * in the inner idle loop, that is, between the rcu_idle_enter() and * the rcu_idle_exit() -- RCU will happily ignore any such read-side * critical sections. However, things like powertop need tracepoints * in the inner idle loop. * * This macro provides the way out: RCU_NONIDLE(do_something_with_RCU()) * will tell RCU that it needs to pay attending, invoke its argument * (in this example, a call to the do_something_with_RCU() function), * and then tell RCU to go back to ignoring this CPU. It is permissible


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