From a593d6edeb0a5a2c6e6919b225cec668a375df52 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Mon, 2 Oct 2006 02:18:53 -0700 Subject: [PATCH] proc: convert do_task_stat() to use lock_task_sighand() Drop tasklist_lock. ->siglock protects almost all interesting data (including sub-threads traversal) except: ->signal->tty protected by tty_mutex ->real_parent the task can't be unhashed while we are holding ->siglock, so ->real_parent can change from under us but we can safely dereference it under rcu_read_lock() ->pgrp/->session we can get inconsistent numbers if the task does sys_setsid/daemonize at the same time. I hope this is acceptable. Signed-off-by: Oleg Nesterov Cc: "Eric W. Biederman" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/proc/array.c | 63 ++++++++++++++++++++++++++++++++------------------------- 1 file changed, 35 insertions(+), 28 deletions(-) diff --git a/fs/proc/array.c b/fs/proc/array.c index 279fbf542c88..35bd39dac247 100644 --- a/fs/proc/array.c +++ b/fs/proc/array.c @@ -321,7 +321,7 @@ static int do_task_stat(struct task_struct *task, char * buffer, int whole) sigset_t sigign, sigcatch; char state; int res; - pid_t ppid, pgid = -1, sid = -1; + pid_t ppid = 0, pgid = -1, sid = -1; int num_threads = 0; struct mm_struct *mm; unsigned long long start_time; @@ -329,8 +329,8 @@ static int do_task_stat(struct task_struct *task, char * buffer, int whole) unsigned long min_flt = 0, maj_flt = 0; cputime_t cutime, cstime, utime, stime; unsigned long rsslim = 0; - struct task_struct *t; char tcomm[sizeof(task->comm)]; + unsigned long flags; state = *get_task_state(task); vsize = eip = esp = 0; @@ -348,15 +348,33 @@ static int do_task_stat(struct task_struct *task, char * buffer, int whole) cutime = cstime = utime = stime = cputime_zero; mutex_lock(&tty_mutex); - read_lock(&tasklist_lock); - if (task->sighand) { - spin_lock_irq(&task->sighand->siglock); - num_threads = atomic_read(&task->signal->count); + rcu_read_lock(); + if (lock_task_sighand(task, &flags)) { + struct signal_struct *sig = task->signal; + struct tty_struct *tty = sig->tty; + + if (tty) { + /* + * sig->tty is not stable, but tty_mutex + * protects us from release_dev(tty) + */ + barrier(); + tty_pgrp = tty->pgrp; + tty_nr = new_encode_dev(tty_devnum(tty)); + } + + num_threads = atomic_read(&sig->count); collect_sigign_sigcatch(task, &sigign, &sigcatch); + cmin_flt = sig->cmin_flt; + cmaj_flt = sig->cmaj_flt; + cutime = sig->cutime; + cstime = sig->cstime; + rsslim = sig->rlim[RLIMIT_RSS].rlim_cur; + /* add up live thread stats at the group level */ if (whole) { - t = task; + struct task_struct *t = task; do { min_flt += t->min_flt; maj_flt += t->maj_flt; @@ -364,31 +382,20 @@ static int do_task_stat(struct task_struct *task, char * buffer, int whole) stime = cputime_add(stime, t->stime); t = next_thread(t); } while (t != task); - } - spin_unlock_irq(&task->sighand->siglock); - } - if (task->signal) { - if (task->signal->tty) { - tty_pgrp = task->signal->tty->pgrp; - tty_nr = new_encode_dev(tty_devnum(task->signal->tty)); + min_flt += sig->min_flt; + maj_flt += sig->maj_flt; + utime = cputime_add(utime, sig->utime); + stime = cputime_add(stime, sig->stime); } + + sid = sig->session; pgid = process_group(task); - sid = task->signal->session; - cmin_flt = task->signal->cmin_flt; - cmaj_flt = task->signal->cmaj_flt; - cutime = task->signal->cutime; - cstime = task->signal->cstime; - rsslim = task->signal->rlim[RLIMIT_RSS].rlim_cur; - if (whole) { - min_flt += task->signal->min_flt; - maj_flt += task->signal->maj_flt; - utime = cputime_add(utime, task->signal->utime); - stime = cputime_add(stime, task->signal->stime); - } + ppid = rcu_dereference(task->real_parent)->tgid; + + unlock_task_sighand(task, &flags); } - ppid = pid_alive(task) ? task->group_leader->real_parent->tgid : 0; - read_unlock(&tasklist_lock); + rcu_read_unlock(); mutex_unlock(&tty_mutex); if (!whole || num_threads<2) -- cgit v1.2.1