From a6bebbc87a8c16eabb6bd5c6fd2d994be0236fba Mon Sep 17 00:00:00 2001 From: Lai Jiangshan Date: Sun, 5 Oct 2008 00:51:15 +0400 Subject: [PATCH] [PATCH] signal, procfs: some lock_task_sighand() users do not need rcu_read_lock() lock_task_sighand() make sure task->sighand is being protected, so we do not need rcu_read_lock(). [ exec() will get task->sighand->siglock before change task->sighand! ] But code using rcu_read_lock() _just_ to protect lock_task_sighand() only appear in procfs. (and some code in procfs use lock_task_sighand() without such redundant protection.) Other subsystem may put lock_task_sighand() into rcu_read_lock() critical region, but these rcu_read_lock() are used for protecting "for_each_process()", "find_task_by_vpid()" etc. , not for protecting lock_task_sighand(). Signed-off-by: Lai Jiangshan [ok from Oleg] Signed-off-by: Alexey Dobriyan --- fs/proc/array.c | 2 -- fs/proc/base.c | 9 +-------- kernel/sched_debug.c | 2 -- 3 files changed, 1 insertion(+), 12 deletions(-) diff --git a/fs/proc/array.c b/fs/proc/array.c index 71c9be59c9c..1c8d7b5d7a1 100644 --- a/fs/proc/array.c +++ b/fs/proc/array.c @@ -261,7 +261,6 @@ static inline void task_sig(struct seq_file *m, struct task_struct *p) sigemptyset(&ignored); sigemptyset(&caught); - rcu_read_lock(); if (lock_task_sighand(p, &flags)) { pending = p->pending.signal; shpending = p->signal->shared_pending.signal; @@ -272,7 +271,6 @@ static inline void task_sig(struct seq_file *m, struct task_struct *p) qlim = p->signal->rlim[RLIMIT_SIGPENDING].rlim_cur; unlock_task_sighand(p, &flags); } - rcu_read_unlock(); seq_printf(m, "Threads:\t%d\n", num_threads); seq_printf(m, "SigQ:\t%lu/%lu\n", qsize, qlim); diff --git a/fs/proc/base.c b/fs/proc/base.c index a28840b11b8..bb63fa1d34a 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -164,7 +164,6 @@ static struct fs_struct *get_fs_struct(struct task_struct *task) static int get_nr_threads(struct task_struct *tsk) { - /* Must be called with the rcu_read_lock held */ unsigned long flags; int count = 0; @@ -471,14 +470,10 @@ static int proc_pid_limits(struct task_struct *task, char *buffer) struct rlimit rlim[RLIM_NLIMITS]; - rcu_read_lock(); - if (!lock_task_sighand(task,&flags)) { - rcu_read_unlock(); + if (!lock_task_sighand(task, &flags)) return 0; - } memcpy(rlim, task->signal->rlim, sizeof(struct rlimit) * RLIM_NLIMITS); unlock_task_sighand(task, &flags); - rcu_read_unlock(); /* * print the file header @@ -3088,9 +3083,7 @@ static int proc_task_getattr(struct vfsmount *mnt, struct dentry *dentry, struct generic_fillattr(inode, stat); if (p) { - rcu_read_lock(); stat->nlink += get_nr_threads(p); - rcu_read_unlock(); put_task_struct(p); } diff --git a/kernel/sched_debug.c b/kernel/sched_debug.c index bbe6b31c3c5..ad958c1ec70 100644 --- a/kernel/sched_debug.c +++ b/kernel/sched_debug.c @@ -333,12 +333,10 @@ void proc_sched_show_task(struct task_struct *p, struct seq_file *m) unsigned long flags; int num_threads = 1; - rcu_read_lock(); if (lock_task_sighand(p, &flags)) { num_threads = atomic_read(&p->signal->count); unlock_task_sighand(p, &flags); } - rcu_read_unlock(); SEQ_printf(m, "%s (%d, #threads: %d)\n", p->comm, p->pid, num_threads); SEQ_printf(m,