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Commit a6bebbc8 authored by Lai Jiangshan's avatar Lai Jiangshan Committed by Alexey Dobriyan
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[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: default avatarLai Jiangshan <laijs@cn.fujitsu.com>
[ok from Oleg]
Signed-off-by: default avatarAlexey Dobriyan <adobriyan@gmail.com>
parent 53167a3e

fs/proc/array.c

+0 −2
Original line number Diff line number Diff line
@@ -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);

fs/proc/base.c

+1 −8
Original line number Diff line number Diff line
@@ -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);

	}

kernel/sched_debug.c

+0 −2
Original line number Diff line number Diff line
@@ -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,