The patch titled
proc_flush_task: flush /proc/tid/task/pid when a sub-thread exits
has been added to the -mm tree. Its filename is
proc_flush_task-flush-proc-tid-task-pid-when-a-sub-thread-exits.patch
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------------------------------------------------------
Subject: proc_flush_task: flush /proc/tid/task/pid when a sub-thread exits
From: Oleg Nesterov <oleg@xxxxxxxxxx>
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" <jleddy@xxxxxxxxxx>
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: Dominic Duval <dduval@xxxxxxxxxx>
Cc: Frank Hirtz <fhirtz@xxxxxxxxxx>
Cc: "Fuller, Johnray" <Johnray.Fuller@xxxxxx>
Cc: Larry Woodman <lwoodman@xxxxxxxxxx>
Cc: Paul Batkowski <pbatkowski@xxxxxxxxxx>
Cc: Roland McGrath <roland@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/proc/base.c | 10 +++-------
1 file changed, 3 insertions(+), 7 deletions(-)
diff -puN fs/proc/base.c~proc_flush_task-flush-proc-tid-task-pid-when-a-sub-thread-exits fs/proc/base.c
--- a/fs/proc/base.c~proc_flush_task-flush-proc-tid-task-pid-when-a-sub-thread-exits
+++ a/fs/proc/base.c
@@ -2601,9 +2601,6 @@ static void proc_flush_task_mnt(struct v
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);
@@ -2660,17 +2657,16 @@ 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];
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
linux-next.patch
getrusage-fill-ru_maxrss-value.patch
getrusage-fill-ru_maxrss-value-update.patch
proc_flush_task-flush-proc-tid-task-pid-when-a-sub-thread-exits.patch
ptrace-__ptrace_detach-do-__wake_up_parent-if-we-reap-the-tracee.patch
do_wait-wakeup-optimization-shift-security_task_wait-from-eligible_child-to-wait_consider_task.patch
do_wait-wakeup-optimization-change-__wake_up_parent-to-use-filtered-wakeup.patch
do_wait-wakeup-optimization-change-__wake_up_parent-to-use-filtered-wakeup-selinux_bprm_committed_creds-use-__wake_up_parent.patch
do_wait-wakeup-optimization-child_wait_callback-check-__wnothread-case.patch
do_wait-optimization-do-not-place-sub-threads-on-task_struct-children-list.patch
wait_consider_task-kill-parent-argument.patch
do_wait-fix-sys_waitid-specific-behaviour.patch
wait_noreap_copyout-check-for-wo_info-=-null.patch
signals-tracehook_notify_jctl-change.patch
utrace-core.patch
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