diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h index 06911b4f717354cc6d0ca40ee261936803abce03..0fcd49d1d51605051641561c4df4db142e37ac4f 100644 --- a/include/linux/interrupt.h +++ b/include/linux/interrupt.h @@ -628,26 +628,21 @@ enum TASKLET_STATE_RUN /* Tasklet is running (SMP only) */ }; -#ifdef CONFIG_SMP +#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT) static inline int tasklet_trylock(struct tasklet_struct *t) { return !test_and_set_bit(TASKLET_STATE_RUN, &(t)->state); } -static inline void tasklet_unlock(struct tasklet_struct *t) -{ - smp_mb__before_atomic(); - clear_bit(TASKLET_STATE_RUN, &(t)->state); -} +void tasklet_unlock(struct tasklet_struct *t); +void tasklet_unlock_wait(struct tasklet_struct *t); +void tasklet_unlock_spin_wait(struct tasklet_struct *t); -static inline void tasklet_unlock_wait(struct tasklet_struct *t) -{ - while (test_bit(TASKLET_STATE_RUN, &(t)->state)) { barrier(); } -} #else -#define tasklet_trylock(t) 1 -#define tasklet_unlock_wait(t) do { } while (0) -#define tasklet_unlock(t) do { } while (0) +static inline int tasklet_trylock(struct tasklet_struct *t) { return 1; } +static inline void tasklet_unlock(struct tasklet_struct *t) { } +static inline void tasklet_unlock_wait(struct tasklet_struct *t) { } +static inline void tasklet_unlock_spin_wait(struct tasklet_struct *t) { } #endif extern void __tasklet_schedule(struct tasklet_struct *t); @@ -672,10 +667,22 @@ static inline void tasklet_disable_nosync(struct tasklet_struct *t) smp_mb__after_atomic(); } +/* + * Do not use in new code. Disabling tasklets from atomic contexts is + * error prone and should be avoided. + */ +static inline void tasklet_disable_in_atomic(struct tasklet_struct *t) +{ + tasklet_disable_nosync(t); + tasklet_unlock_spin_wait(t); + smp_mb(); +} + static inline void tasklet_disable(struct tasklet_struct *t) { tasklet_disable_nosync(t); - tasklet_unlock_wait(t); + /* Spin wait until all atomic users are converted */ + tasklet_unlock_spin_wait(t); smp_mb(); } diff --git a/kernel/softirq.c b/kernel/softirq.c index d5bfd5e661fcd6cb20217400da612fc8a43b892f..fcb201ceed71200e807a4fe80061fcf098045863 100644 --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -25,6 +25,7 @@ #include #include #include +#include #define CREATE_TRACE_POINTS #include @@ -529,6 +530,16 @@ void __tasklet_hi_schedule(struct tasklet_struct *t) } EXPORT_SYMBOL(__tasklet_hi_schedule); +static inline bool tasklet_clear_sched(struct tasklet_struct *t) +{ + if (test_and_clear_bit(TASKLET_STATE_SCHED, &t->state)) { + wake_up_var(&t->state); + return true; + } + + return false; +} + static void tasklet_action_common(struct softirq_action *a, struct tasklet_head *tl_head, unsigned int softirq_nr) @@ -548,8 +559,7 @@ static void tasklet_action_common(struct softirq_action *a, if (tasklet_trylock(t)) { if (!atomic_read(&t->count)) { - if (!test_and_clear_bit(TASKLET_STATE_SCHED, - &t->state)) + if (!tasklet_clear_sched(t)) BUG(); if (t->use_callback) t->callback(t); @@ -604,21 +614,62 @@ void tasklet_init(struct tasklet_struct *t, } EXPORT_SYMBOL(tasklet_init); +#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT) +/* + * Do not use in new code. Waiting for tasklets from atomic contexts is + * error prone and should be avoided. + */ +void tasklet_unlock_spin_wait(struct tasklet_struct *t) +{ + while (test_bit(TASKLET_STATE_RUN, &(t)->state)) { + if (IS_ENABLED(CONFIG_PREEMPT_RT)) { + /* + * Prevent a live lock when current preempted soft + * interrupt processing or prevents ksoftirqd from + * running. If the tasklet runs on a different CPU + * then this has no effect other than doing the BH + * disable/enable dance for nothing. + */ + local_bh_disable(); + local_bh_enable(); + } else { + cpu_relax(); + } + } +} +EXPORT_SYMBOL(tasklet_unlock_spin_wait); +#endif + void tasklet_kill(struct tasklet_struct *t) { if (in_interrupt()) pr_notice("Attempt to kill tasklet from interrupt\n"); - while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) { - do { - yield(); - } while (test_bit(TASKLET_STATE_SCHED, &t->state)); - } + while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) + wait_var_event(&t->state, !test_bit(TASKLET_STATE_SCHED, &t->state)); + tasklet_unlock_wait(t); - clear_bit(TASKLET_STATE_SCHED, &t->state); + tasklet_clear_sched(t); } EXPORT_SYMBOL(tasklet_kill); +#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT) +void tasklet_unlock(struct tasklet_struct *t) +{ + smp_mb__before_atomic(); + clear_bit(TASKLET_STATE_RUN, &t->state); + smp_mb__after_atomic(); + wake_up_var(&t->state); +} +EXPORT_SYMBOL_GPL(tasklet_unlock); + +void tasklet_unlock_wait(struct tasklet_struct *t) +{ + wait_var_event(&t->state, !test_bit(TASKLET_STATE_RUN, &t->state)); +} +EXPORT_SYMBOL_GPL(tasklet_unlock_wait); +#endif + void __init softirq_init(void) { int cpu;