diff options
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/cpuset.h | 47 | ||||
| -rw-r--r-- | include/linux/init_task.h | 8 | ||||
| -rw-r--r-- | include/linux/sched.h | 2 |
3 files changed, 29 insertions, 28 deletions
diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h index e9eaec522655..7a7e5fd2a277 100644 --- a/include/linux/cpuset.h +++ b/include/linux/cpuset.h @@ -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); } @@ -234,12 +225,14 @@ 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 */ diff --git a/include/linux/init_task.h b/include/linux/init_task.h index f994d51f70f2..e4baff5f7ff4 100644 --- a/include/linux/init_task.h +++ b/include/linux/init_task.h @@ -29,6 +29,13 @@ extern struct fs_struct init_fs; #define INIT_GROUP_RWSEM(sig) #endif +#ifdef CONFIG_CPUSETS +#define INIT_CPUSET_SEQ \ + .mems_allowed_seq = SEQCNT_ZERO, +#else +#define INIT_CPUSET_SEQ +#endif + #define INIT_SIGNALS(sig) { \ .nr_threads = 1, \ .wait_chldexit = __WAIT_QUEUE_HEAD_INITIALIZER(sig.wait_chldexit),\ @@ -192,6 +199,7 @@ extern struct cred init_cred; INIT_FTRACE_GRAPH \ INIT_TRACE_RECURSION \ INIT_TASK_RCU_PREEMPT(tsk) \ + INIT_CPUSET_SEQ \ } diff --git a/include/linux/sched.h b/include/linux/sched.h index e074e1e54f85..0c147a4260a5 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1514,7 +1514,7 @@ struct task_struct { #endif #ifdef CONFIG_CPUSETS nodemask_t mems_allowed; /* Protected by alloc_lock */ - int mems_allowed_change_disable; + seqcount_t mems_allowed_seq; /* Seqence no to catch updates */ int cpuset_mem_spread_rotor; int cpuset_slab_spread_rotor; #endif |