From b3426599af9524104be6938bcb1fcaab314781c7 Mon Sep 17 00:00:00 2001 From: Paul Jackson Date: Mon, 12 Sep 2005 04:30:30 -0700 Subject: [PATCH] cpuset semaphore depth check optimize Optimize the deadlock avoidance check on the global cpuset semaphore cpuset_sem. Instead of adding a depth counter to the task struct of each task, rather just two words are enough, one to store the depth and the other the current cpuset_sem holder. Thanks to Nikita Danilov for the idea. Signed-off-by: Paul Jackson [ We may want to change this further, but at least it's now a totally internal decision to the cpusets code ] Signed-off-by: Linus Torvalds --- include/linux/sched.h | 1 - kernel/cpuset.c | 13 +++++++++---- 2 files changed, 9 insertions(+), 5 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index ed3bb19..38c8654 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -785,7 +785,6 @@ struct task_struct { short il_next; #endif #ifdef CONFIG_CPUSETS - short cpuset_sem_nest_depth; struct cpuset *cpuset; nodemask_t mems_allowed; int cpuset_mems_generation; diff --git a/kernel/cpuset.c b/kernel/cpuset.c index 407b5f0..79866bc 100644 --- a/kernel/cpuset.c +++ b/kernel/cpuset.c @@ -180,6 +180,8 @@ static struct super_block *cpuset_sb = NULL; */ static DECLARE_MUTEX(cpuset_sem); +static struct task_struct *cpuset_sem_owner; +static int cpuset_sem_depth; /* * The global cpuset semaphore cpuset_sem can be needed by the @@ -200,16 +202,19 @@ static DECLARE_MUTEX(cpuset_sem); static inline void cpuset_down(struct semaphore *psem) { - if (current->cpuset_sem_nest_depth == 0) + if (cpuset_sem_owner != current) { down(psem); - current->cpuset_sem_nest_depth++; + cpuset_sem_owner = current; + } + cpuset_sem_depth++; } static inline void cpuset_up(struct semaphore *psem) { - current->cpuset_sem_nest_depth--; - if (current->cpuset_sem_nest_depth == 0) + if (--cpuset_sem_depth == 0) { + cpuset_sem_owner = NULL; up(psem); + } } /* -- cgit v1.1