From a183561567b5446d3362b4839bd4f744f4b2af1e Mon Sep 17 00:00:00 2001 From: Srivatsa Vaddagiri Date: Fri, 25 Jan 2008 21:08:00 +0100 Subject: [PATCH] sched: introduce a mutex and corresponding API to serialize access to doms_curarray doms_cur[] array represents various scheduling domains which are mutually exclusive. Currently cpusets code can modify this array (by calling partition_sched_domains()) as a result of user modifying sched_load_balance flag for various cpusets. This patch introduces a mutex and corresponding API (only when CONFIG_FAIR_GROUP_SCHED is defined) which allows a reader to safely read the doms_cur[] array w/o worrying abt concurrent modifications to the array. The fair group scheduler code (introduced in next patch of this series) makes use of this mutex to walk thr' doms_cur[] array while rebalancing shares of task groups across cpus. Signed-off-by: Srivatsa Vaddagiri Signed-off-by: Ingo Molnar --- kernel/sched.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/kernel/sched.c b/kernel/sched.c index c915f3e6e593..d9585f15043f 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -185,6 +185,9 @@ static struct cfs_rq *init_cfs_rq_p[NR_CPUS]; */ static DEFINE_MUTEX(task_group_mutex); +/* doms_cur_mutex serializes access to doms_cur[] array */ +static DEFINE_MUTEX(doms_cur_mutex); + /* Default task group. * Every task in system belong to this group at bootup. */ @@ -234,11 +237,23 @@ static inline void unlock_task_group_list(void) mutex_unlock(&task_group_mutex); } +static inline void lock_doms_cur(void) +{ + mutex_lock(&doms_cur_mutex); +} + +static inline void unlock_doms_cur(void) +{ + mutex_unlock(&doms_cur_mutex); +} + #else static inline void set_task_cfs_rq(struct task_struct *p, unsigned int cpu) { } static inline void lock_task_group_list(void) { } static inline void unlock_task_group_list(void) { } +static inline void lock_doms_cur(void) { } +static inline void unlock_doms_cur(void) { } #endif /* CONFIG_FAIR_GROUP_SCHED */ @@ -6543,6 +6558,8 @@ void partition_sched_domains(int ndoms_new, cpumask_t *doms_new) { int i, j; + lock_doms_cur(); + /* always unregister in case we don't destroy any domains */ unregister_sched_domain_sysctl(); @@ -6583,6 +6600,8 @@ match2: ndoms_cur = ndoms_new; register_sched_domain_sysctl(); + + unlock_doms_cur(); } #if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)