Messages in this thread Patch in this message |  | | | Date | Tue, 27 Nov 2007 10:51:21 +0530 | | From | Srivatsa Vaddagiri <> | | Subject | [Patch 4/5] sched: introduce a mutex and corresponding API to serialize access to doms_cur[] array |
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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 <vatsa@linux.vnet.ibm.com>
--- kernel/sched.c | 19 +++++++++++++++++++ 1 files changed, 19 insertions(+) Index: current/kernel/sched.c =================================================================== --- current.orig/kernel/sched.c +++ current/kernel/sched.c @@ -186,6 +186,9 @@ static struct cfs_rq *init_cfs_rq_p[NR_C */ 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. */ @@ -236,11 +239,23 @@ static inline void unlock_task_group_lis 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 */ @@ -6547,6 +6562,8 @@ void partition_sched_domains(int ndoms_n { int i, j; + lock_doms_cur(); + /* always unregister in case we don't destroy any domains */ unregister_sched_domain_sysctl(); @@ -6587,6 +6604,8 @@ match2: ndoms_cur = ndoms_new; register_sched_domain_sysctl(); + + unlock_doms_cur(); } #if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
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