From 9b4d1cbef8f41aff2b3e4ca31f566c071fe601de Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 22 Sep 2009 16:45:34 -0700 Subject: proc_flush_task: flush /proc/tid/task/pid when a sub-thread exits The exiting sub-thread flushes /proc/pid only, but this doesn't buy too much: ps and friends mostly use /proc/tid/task/pid. Remove "if (thread_group_leader())" checks from proc_flush_task() path, this means we always remove /proc/tid/task/pid dentry on exit, and this actually matches the comment above proc_flush_task(). The test-case: static void* tfunc(void *arg) { char name[256]; sprintf(name, "/proc/%d/task/%ld/status", getpid(), gettid()); close(open(name, O_RDONLY)); return NULL; } int main(void) { pthread_t t; for (;;) { if (!pthread_create(&t, NULL, &tfunc, NULL)) pthread_join(t, NULL); } } slabtop shows that pid/proc_inode_cache/etc grow quickly and "indefinitely" until the task is killed or shrink_slab() is called, not good. And the main thread needs a lot of time to exit. The same can happen if something like "ps -efL" runs continuously, while some application spawns short-living threads. Reported-by: "James M. Leddy" Signed-off-by: Oleg Nesterov Cc: Alexey Dobriyan Cc: "Eric W. Biederman" Cc: Dominic Duval Cc: Frank Hirtz Cc: "Fuller, Johnray" Cc: Larry Woodman Cc: Paul Batkowski Cc: Roland McGrath Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/proc/base.c | 10 +++------- 1 file changed, 3 insertions(+), 7 deletions(-) diff --git a/fs/proc/base.c b/fs/proc/base.c index 69bb70351b9..5bc587049b3 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -2604,9 +2604,6 @@ static void proc_flush_task_mnt(struct vfsmount *mnt, pid_t pid, pid_t tgid) dput(dentry); } - if (tgid == 0) - goto out; - name.name = buf; name.len = snprintf(buf, sizeof(buf), "%d", tgid); leader = d_hash_and_lookup(mnt->mnt_root, &name); @@ -2663,17 +2660,16 @@ out: void proc_flush_task(struct task_struct *task) { int i; - struct pid *pid, *tgid = NULL; + struct pid *pid, *tgid; struct upid *upid; pid = task_pid(task); - if (thread_group_leader(task)) - tgid = task_tgid(task); + tgid = task_tgid(task); for (i = 0; i <= pid->level; i++) { upid = &pid->numbers[i]; proc_flush_task_mnt(upid->ns->proc_mnt, upid->nr, - tgid ? tgid->numbers[i].nr : 0); + tgid->numbers[i].nr); } upid = &pid->numbers[pid->level]; -- cgit v1.2.3