path: root/kernel
diff options
authorAndrew Morton <>2006-03-25 03:07:48 -0800
committerLinus Torvalds <>2006-03-25 08:22:57 -0800
commit05eeae208d08a05a6980cf2ff61f02843c0955fd (patch)
treebe6c6c4e16cfac07edf437a1f74ef027ada8ccc7 /kernel
parentc1f5a1944657ba6abe375e3bb2a3238a46849f70 (diff)
[PATCH] find_task_by_pid() needs tasklist_lock
A couple of places are forgetting to take it. The kswapd case is probably unimportant. keventd_create_kthread() was racy. The whole thing is a bit flakey: you start a kernel thread, get its pid from kernel_thread() then look up its task_struct. a) It assumes that pid recycling takes a "long" time. b) We get a task_struct but no reference was taken on it. The owner of the kswapd and kthread task_struct*'s must assume that the new thread won't exit unexpectedly. Because if it does, they're left holding dead memory and any attempt to control or stop that task will crash. Cc: Christoph Hellwig <> Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'kernel')
1 files changed, 2 insertions, 0 deletions
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 6a5373868a98..c5f3c6613b6d 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -115,7 +115,9 @@ static void keventd_create_kthread(void *_create)
create->result = ERR_PTR(pid);
} else {
+ read_lock(&tasklist_lock);
create->result = find_task_by_pid(pid);
+ read_unlock(&tasklist_lock);