diff options
Diffstat (limited to 'include/linux/cpuset.h')
| -rw-r--r-- | include/linux/cpuset.h | 53 |
1 files changed, 22 insertions, 31 deletions
diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h index e9eaec522655..668f66baac7b 100644 --- a/include/linux/cpuset.h +++ b/include/linux/cpuset.h @@ -22,7 +22,7 @@ extern int cpuset_init(void); extern void cpuset_init_smp(void); extern void cpuset_update_active_cpus(void); extern void cpuset_cpus_allowed(struct task_struct *p, struct cpumask *mask); -extern int cpuset_cpus_allowed_fallback(struct task_struct *p); +extern void cpuset_cpus_allowed_fallback(struct task_struct *p); extern nodemask_t cpuset_mems_allowed(struct task_struct *p); #define cpuset_current_mems_allowed (current->mems_allowed) void cpuset_init_current_mems_allowed(void); @@ -89,42 +89,33 @@ extern void rebuild_sched_domains(void); extern void cpuset_print_task_mems_allowed(struct task_struct *p); /* - * reading current mems_allowed and mempolicy in the fastpath must protected - * by get_mems_allowed() + * get_mems_allowed is required when making decisions involving mems_allowed + * such as during page allocation. mems_allowed can be updated in parallel + * and depending on the new value an operation can fail potentially causing + * process failure. A retry loop with get_mems_allowed and put_mems_allowed + * prevents these artificial failures. */ -static inline void get_mems_allowed(void) +static inline unsigned int get_mems_allowed(void) { - current->mems_allowed_change_disable++; - - /* - * ensure that reading mems_allowed and mempolicy happens after the - * update of ->mems_allowed_change_disable. - * - * the write-side task finds ->mems_allowed_change_disable is not 0, - * and knows the read-side task is reading mems_allowed or mempolicy, - * so it will clear old bits lazily. - */ - smp_mb(); + return read_seqcount_begin(¤t->mems_allowed_seq); } -static inline void put_mems_allowed(void) +/* + * If this returns false, the operation that took place after get_mems_allowed + * may have failed. It is up to the caller to retry the operation if + * appropriate. + */ +static inline bool put_mems_allowed(unsigned int seq) { - /* - * ensure that reading mems_allowed and mempolicy before reducing - * mems_allowed_change_disable. - * - * the write-side task will know that the read-side task is still - * reading mems_allowed or mempolicy, don't clears old bits in the - * nodemask. - */ - smp_mb(); - --ACCESS_ONCE(current->mems_allowed_change_disable); + return !read_seqcount_retry(¤t->mems_allowed_seq, seq); } static inline void set_mems_allowed(nodemask_t nodemask) { task_lock(current); + write_seqcount_begin(¤t->mems_allowed_seq); current->mems_allowed = nodemask; + write_seqcount_end(¤t->mems_allowed_seq); task_unlock(current); } @@ -144,10 +135,8 @@ static inline void cpuset_cpus_allowed(struct task_struct *p, cpumask_copy(mask, cpu_possible_mask); } -static inline int cpuset_cpus_allowed_fallback(struct task_struct *p) +static inline void cpuset_cpus_allowed_fallback(struct task_struct *p) { - do_set_cpus_allowed(p, cpu_possible_mask); - return cpumask_any(cpu_active_mask); } static inline nodemask_t cpuset_mems_allowed(struct task_struct *p) @@ -234,12 +223,14 @@ static inline void set_mems_allowed(nodemask_t nodemask) { } -static inline void get_mems_allowed(void) +static inline unsigned int get_mems_allowed(void) { + return 0; } -static inline void put_mems_allowed(void) +static inline bool put_mems_allowed(unsigned int seq) { + return true; } #endif /* !CONFIG_CPUSETS */ |