Re: [PATCH 6.6] fs/proc: do_task_stat: use sig->stats_lock to gather the threads/children stats

[Sasha Levin <sashal@kernel.org>]

[ Sasha's backport helper bot ]

Hi,

The upstream commit SHA1 provided is correct: 7601df8031fd67310af891897ef6cc0df4209305

WARNING: Author mismatch between patch and upstream commit:
Backport author: Bin Lan <bin.lan.cn@windriver.com>
Commit author: Oleg Nesterov <oleg@redhat.com>


Status in newer kernel trees:
6.12.y | Present (exact SHA1)
6.11.y | Present (exact SHA1)
6.6.y | Not found

Note: The patch differs from the upstream commit:
---
--- -	2024-11-25 08:56:48.440504041 -0500
+++ /tmp/tmp.DBppGejMK4	2024-11-25 08:56:48.433034088 -0500
@@ -1,3 +1,5 @@
+[ Upstream commit 7601df8031fd67310af891897ef6cc0df4209305 ]
+
 lock_task_sighand() can trigger a hard lockup.  If NR_CPUS threads call
 do_task_stat() at the same time and the process has NR_THREADS, it will
 spin with irqs disabled O(NR_CPUS * NR_THREADS) time.
@@ -12,12 +14,14 @@
 Cc: Eric W. Biederman <ebiederm@xmission.com>
 Cc: <stable@vger.kernel.org>
 Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
+[ Resolve minor conflicts ]
+Signed-off-by: Bin Lan <bin.lan.cn@windriver.com>
 ---
- fs/proc/array.c | 58 +++++++++++++++++++++++++++----------------------
- 1 file changed, 32 insertions(+), 26 deletions(-)
+ fs/proc/array.c | 57 +++++++++++++++++++++++++++----------------------
+ 1 file changed, 32 insertions(+), 25 deletions(-)
 
 diff --git a/fs/proc/array.c b/fs/proc/array.c
-index 45ba918638084..34a47fb0c57f2 100644
+index 37b8061d84bb..34a47fb0c57f 100644
 --- a/fs/proc/array.c
 +++ b/fs/proc/array.c
 @@ -477,13 +477,13 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
@@ -51,7 +55,7 @@
  		if (sig->tty) {
  			struct pid *pgrp = tty_get_pgrp(sig->tty);
  			tty_pgrp = pid_nr_ns(pgrp, ns);
-@@ -527,27 +523,9 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
+@@ -527,26 +523,9 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
  		num_threads = get_nr_threads(task);
  		collect_sigign_sigcatch(task, &sigign, &sigcatch);
  
@@ -64,13 +68,12 @@
  
 -		/* add up live thread stats at the group level */
  		if (whole) {
--			struct task_struct *t;
--
--			__for_each_thread(sig, t) {
+-			struct task_struct *t = task;
+-			do {
 -				min_flt += t->min_flt;
 -				maj_flt += t->maj_flt;
 -				gtime += task_gtime(t);
--			}
+-			} while_each_thread(task, t);
 -
 -			min_flt += sig->min_flt;
 -			maj_flt += sig->maj_flt;
@@ -79,7 +82,7 @@
  			if (sig->flags & (SIGNAL_GROUP_EXIT | SIGNAL_STOP_STOPPED))
  				exit_code = sig->group_exit_code;
  		}
-@@ -562,6 +540,34 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
+@@ -561,6 +540,34 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
  	if (permitted && (!whole || num_threads < 2))
  		wchan = !task_is_running(task);
  
@@ -114,3 +117,6 @@
  	if (whole) {
  		thread_group_cputime_adjusted(task, &utime, &stime);
  	} else {
+-- 
+2.43.0
+
---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-6.6.y        |  Success    |  Success   |