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Subject[PATCH 06/26] rlimit: Remove unnecessary grab of tasklist_lock
There is no reason to take the tasklist lock here.  The sighand
structure is never referenced and and tsk->signal is guaranteed
to stick around until tsk is freed. Further update_rlimit_cpu
does not need the tasklist_lock. And the rlim_lock is used
to guarantee mutual exclusion.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
kernel/sys.c | 10 +---------
1 file changed, 1 insertion(+), 9 deletions(-)

diff --git a/kernel/sys.c b/kernel/sys.c
index 8a94b4eabcaa..705f14b28134 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1380,13 +1380,6 @@ int do_prlimit(struct task_struct *tsk, unsigned int resource,
return -EPERM;
}

- /* protect tsk->signal and tsk->sighand from disappearing */
- read_lock(&tasklist_lock);
- if (!tsk->sighand) {
- retval = -ESRCH;
- goto out;
- }
-
rlim = tsk->signal->rlim + resource;
task_lock(tsk->group_leader);
if (new_rlim) {
@@ -1425,8 +1418,7 @@ int do_prlimit(struct task_struct *tsk, unsigned int resource,
new_rlim->rlim_cur != RLIM_INFINITY &&
IS_ENABLED(CONFIG_POSIX_TIMERS))
update_rlimit_cpu(tsk, new_rlim->rlim_cur);
-out:
- read_unlock(&tasklist_lock);
+
return retval;
}

--
2.10.1
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