Re: [PATCH 2.6.13.1] Patch for invisible threads

Sripathi Kodi
2005-09-14T01:47:37Z

Linus Torvalds wrote:

> I don't think this is wrong per se, but you shouldn't take the tasklist
> lock normally. You're better off just doing

Linus,

I incarporated the path that doesn't hold tasklist lock unnecessarily. The
patch is below. This seems to work without any problems for me.

If the decision is to remove ->permission, I can send a small patch I have
that removes .permission entry from proc_task_inode_operations. Either way
fixes the problem I found.

Thanks and regards,
Sripathi.

Signed-off-by: Sripathi Kodi <sripathik@in.ibm.com>

--- linux-2.6.13.1-orig/fs/proc/base.c 2005-09-14 03:46:22.000000000 -0500
+++ linux-2.6.13.1/fs/proc/base.c 2005-09-14 03:48:35.000000000 -0500
@@ -275,11 +275,33 @@ static int proc_root_link(struct inode *
{
struct fs_struct *fs;
int result = -ENOENT;
- task_lock(proc_task(inode));
- fs = proc_task(inode)->fs;
- if(fs)
+ struct task_struct *leader = proc_task(inode);
+
+ task_lock(leader);
+ fs = leader->fs;
+ if (fs) {
atomic_inc(&fs->count);
- task_unlock(proc_task(inode));
+ task_unlock(leader);
+ } else {
+ /* Try to get fs from sub-threads */
+ task_unlock(leader);
+ struct task_struct *task = leader;
+ read_lock(&tasklist_lock);
+ if (pid_alive(task)) {
+ while ((task = next_thread(task)) != leader) {
+ task_lock(task);
+ fs = task->fs;
+ if (fs) {
+ atomic_inc(&fs->count);
+ task_unlock(task);
+ break;
+ }
+ task_unlock(task);
+ }
+ }
+ read_unlock(&tasklist_lock);
+ }
+
if (fs) {
read_lock(&fs->lock);
*mnt = mntget(fs->rootmnt);