The patch titled
proc: drop tasklist lock in task_state()
has been added to the -mm tree. Its filename is
proc-drop-tasklist-lock-in-task_state.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: proc: drop tasklist lock in task_state()
From: Oleg Nesterov <oleg@xxxxxxxxxx>
task_state() needs tasklist_lock to protect ->parent/->real_parent. However
task->parent points to nowhere only when the actions below happen in order
1) release_task(task)
2) release_task(task->parent)
3) a grace period passed
But 3) implies that the memory ops from 1) should be finished, so pid_alive()
can't be true in such a case.
Otherwise, we don't care if ->parent/->real_parent changes under us.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
fs/proc/array.c | 11 +++++------
1 files changed, 5 insertions(+), 6 deletions(-)
diff -puN fs/proc/array.c~proc-drop-tasklist-lock-in-task_state fs/proc/array.c
--- a/fs/proc/array.c~proc-drop-tasklist-lock-in-task_state
+++ a/fs/proc/array.c
@@ -162,7 +162,7 @@ static inline char * task_state(struct t
int g;
struct fdtable *fdt = NULL;
- read_lock(&tasklist_lock);
+ rcu_read_lock();
buffer += sprintf(buffer,
"State:\t%s\n"
"SleepAVG:\t%lu%%\n"
@@ -174,14 +174,13 @@ static inline char * task_state(struct t
"Gid:\t%d\t%d\t%d\t%d\n",
get_task_state(p),
(p->sleep_avg/1024)*100/(1020000000/1024),
- p->tgid,
- p->pid, pid_alive(p) ? p->group_leader->real_parent->tgid : 0,
- pid_alive(p) && p->ptrace ? p->parent->pid : 0,
+ p->tgid, p->pid,
+ pid_alive(p) ? rcu_dereference(p->real_parent)->tgid : 0,
+ pid_alive(p) && p->ptrace ? rcu_dereference(p->parent)->pid : 0,
p->uid, p->euid, p->suid, p->fsuid,
p->gid, p->egid, p->sgid, p->fsgid);
- read_unlock(&tasklist_lock);
+
task_lock(p);
- rcu_read_lock();
if (p->files)
fdt = files_fdtable(p->files);
buffer += sprintf(buffer,
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
git-block.patch
pid-implement-transfer_pid-and-use-it-to-simplify-de_thread.patch
pid-remove-temporary-debug-code-in-attach_pid.patch
rtmutex-clean-up-and-remove-some-extra-spinlocks.patch
rtmutex-clean-up-and-remove-some-extra-spinlocks-more.patch
elf_core_dump-dont-take-tasklist_lock.patch
elf_fdpic_core_dump-dont-take-tasklist_lock.patch
has_stopped_jobs-cleanup.patch
__dequeue_signal-cleanup.patch
do_sched_setscheduler-dont-take-tasklist_lock.patch
introduce-is_rt_policy-helper.patch
sched_setscheduler-fix-policy-checks.patch
reparent_to_init-use-has_rt_policy.patch
copy_process-cosmetic-ioprio-tweak.patch
futex_find_get_task-dont-take-tasklist_lock.patch
sys_get_robust_list-dont-take-tasklist_lock.patch
set-exit_dead-state-in-do_exit-not-in-schedule.patch
kill-pf_dead-flag.patch
introduce-task_dead-state.patch
select_bad_process-kill-a-bogus-pf_dead-task_dead-check.patch
select_bad_process-cleanup-releasing-check.patch
oom_kill_task-cleanup-mm-checks.patch
audit-accounting-tty-locking.patch
proc-readdir-race-fix-take-3-race-fix.patch
simplify-pid-iterators.patch
proc-convert-task_sig-to-use-lock_task_sighand.patch
proc-convert-do_task_stat-to-use-lock_task_sighand.patch
proc-drop-tasklist-lock-in-task_state.patch
proc-properly-compute-tgid_offset.patch
proc-remove-trailing-blank-entry-from-pid_entry-arrays.patch
proc-remove-the-useless-smp-safe-comments-from-proc.patch
proc-comment-what-proc_fill_cache-does.patch
rcu-simplify-improve-batch-tuning.patch
pidhash-temporary-debug-checks.patch
-
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