Subject: sched: Generic migrate_disable From: Peter Zijlstra Date: Thu Aug 11 15:14:58 CEST 2011 Make migrate_disable() be a preempt_disable() for !rt kernels. This allows generic code to use it but still enforces that these code sections stay relatively small. A preemptible migrate_disable() accessible for general use would allow people growing arbitrary per-cpu crap instead of clean these things up. Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/n/tip-275i87sl8e1jcamtchmehonm@git.kernel.org --- include/linux/preempt.h | 21 +++++++++------------ include/linux/sched.h | 13 +++++++++++++ include/linux/smp.h | 9 ++------- kernel/sched.c | 6 ++++-- kernel/trace/trace.c | 2 +- lib/smp_processor_id.c | 2 +- 6 files changed, 30 insertions(+), 23 deletions(-) Index: linux-3.2/include/linux/preempt.h =================================================================== --- linux-3.2.orig/include/linux/preempt.h +++ linux-3.2/include/linux/preempt.h @@ -108,28 +108,25 @@ do { \ #endif /* CONFIG_PREEMPT_COUNT */ -#ifdef CONFIG_SMP -extern void migrate_disable(void); -extern void migrate_enable(void); -#else -# define migrate_disable() do { } while (0) -# define migrate_enable() do { } while (0) -#endif - #ifdef CONFIG_PREEMPT_RT_FULL # define preempt_disable_rt() preempt_disable() # define preempt_enable_rt() preempt_enable() # define preempt_disable_nort() do { } while (0) # define preempt_enable_nort() do { } while (0) -# define migrate_disable_rt() migrate_disable() -# define migrate_enable_rt() migrate_enable() +# ifdef CONFIG_SMP + extern void migrate_disable(void); + extern void migrate_enable(void); +# else /* CONFIG_SMP */ +# define migrate_disable() do { } while (0) +# define migrate_enable() do { } while (0) +# endif /* CONFIG_SMP */ #else # define preempt_disable_rt() do { } while (0) # define preempt_enable_rt() do { } while (0) # define preempt_disable_nort() preempt_disable() # define preempt_enable_nort() preempt_enable() -# define migrate_disable_rt() do { } while (0) -# define migrate_enable_rt() do { } while (0) +# define migrate_disable() preempt_disable() +# define migrate_enable() preempt_enable() #endif #ifdef CONFIG_PREEMPT_NOTIFIERS Index: linux-3.2/include/linux/sched.h =================================================================== --- linux-3.2.orig/include/linux/sched.h +++ linux-3.2/include/linux/sched.h @@ -1259,7 +1259,9 @@ struct task_struct { #endif unsigned int policy; +#ifdef CONFIG_PREEMPT_RT_FULL int migrate_disable; +#endif cpumask_t cpus_allowed; #ifdef CONFIG_PREEMPT_RCU @@ -2677,11 +2679,22 @@ static inline void set_task_cpu(struct t #endif /* CONFIG_SMP */ +static inline int __migrate_disabled(struct task_struct *p) +{ +#ifdef CONFIG_PREEMPT_RT_FULL + return p->migrate_disable; +#else + return 0; +#endif +} + /* Future-safe accessor for struct task_struct's cpus_allowed. */ static inline const struct cpumask *tsk_cpus_allowed(struct task_struct *p) { +#ifdef CONFIG_PREEMPT_RT_FULL if (p->migrate_disable) return cpumask_of(task_cpu(p)); +#endif return &p->cpus_allowed; } Index: linux-3.2/include/linux/smp.h =================================================================== --- linux-3.2.orig/include/linux/smp.h +++ linux-3.2/include/linux/smp.h @@ -172,13 +172,8 @@ smp_call_function_any(const struct cpuma #define get_cpu() ({ preempt_disable(); smp_processor_id(); }) #define put_cpu() preempt_enable() -#ifndef CONFIG_PREEMPT_RT_FULL -# define get_cpu_light() get_cpu() -# define put_cpu_light() put_cpu() -#else -# define get_cpu_light() ({ migrate_disable(); smp_processor_id(); }) -# define put_cpu_light() migrate_enable() -#endif +#define get_cpu_light() ({ migrate_disable(); smp_processor_id(); }) +#define put_cpu_light() migrate_enable() /* * Callback to arch code if there's nosmp or maxcpus=0 on the Index: linux-3.2/kernel/sched.c =================================================================== --- linux-3.2.orig/kernel/sched.c +++ linux-3.2/kernel/sched.c @@ -6224,7 +6224,7 @@ static inline void sched_init_granularit #ifdef CONFIG_SMP void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask) { - if (!p->migrate_disable) { + if (!__migrate_disabled(p)) { if (p->sched_class && p->sched_class->set_cpus_allowed) p->sched_class->set_cpus_allowed(p, new_mask); p->rt.nr_cpus_allowed = cpumask_weight(new_mask); @@ -6280,7 +6280,7 @@ int set_cpus_allowed_ptr(struct task_str do_set_cpus_allowed(p, new_mask); /* Can the task run on the task's current CPU? If so, we're done */ - if (cpumask_test_cpu(task_cpu(p), new_mask) || p->migrate_disable) + if (cpumask_test_cpu(task_cpu(p), new_mask) || __migrate_disabled(p)) goto out; dest_cpu = cpumask_any_and(cpu_active_mask, new_mask); @@ -6299,6 +6299,7 @@ out: } EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr); +#ifdef CONFIG_PREEMPT_RT_FULL void migrate_disable(void) { struct task_struct *p = current; @@ -6391,6 +6392,7 @@ void migrate_enable(void) preempt_enable(); } EXPORT_SYMBOL_GPL(migrate_enable); +#endif /* CONFIG_PREEMPT_RT_FULL */ /* * Move (not current) task off this cpu, onto dest cpu. We're doing Index: linux-3.2/kernel/trace/trace.c =================================================================== --- linux-3.2.orig/kernel/trace/trace.c +++ linux-3.2/kernel/trace/trace.c @@ -1124,7 +1124,7 @@ tracing_generic_entry_update(struct trac ((pc & SOFTIRQ_MASK) ? TRACE_FLAG_SOFTIRQ : 0) | (need_resched() ? TRACE_FLAG_NEED_RESCHED : 0); - entry->migrate_disable = (tsk) ? tsk->migrate_disable & 0xFF : 0; + entry->migrate_disable = (tsk) ? __migrate_disabled(tsk) & 0xFF : 0; } EXPORT_SYMBOL_GPL(tracing_generic_entry_update); Index: linux-3.2/lib/smp_processor_id.c =================================================================== --- linux-3.2.orig/lib/smp_processor_id.c +++ linux-3.2/lib/smp_processor_id.c @@ -41,7 +41,7 @@ notrace unsigned int debug_smp_processor printk(KERN_ERR "BUG: using smp_processor_id() in preemptible [%08x %08x] " "code: %s/%d\n", preempt_count() - 1, - current->migrate_disable, current->comm, current->pid); + __migrate_disabled(current), current->comm, current->pid); print_symbol("caller is %s\n", (long)__builtin_return_address(0)); dump_stack();