From: Paul Jackson Date: Mon, 12 Sep 2005 11:30:30 +0000 (-0700) Subject: [PATCH] cpuset semaphore depth check optimize X-Git-Tag: v2.6.14-rc1~88 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b3426599af9524104be6938bcb1fcaab314781c7;p=linux-2.6 [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 --- diff --git a/include/linux/sched.h b/include/linux/sched.h index ed3bb19d13..38c8654aaa 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 407b5f0a8c..79866bc6b3 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); + } } /*