[PATCH 4.4 42/46] proc: add a schedule point in proc_pid_readdir()

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet@xxxxxxxxxx>


[ Upstream commit 3ba4bceef23206349d4130ddf140819b365de7c8 ]

We have seen proc_pid_readdir() invocations holding cpu for more than 50
ms.  Add a cond_resched() to be gentle with other tasks.

[akpm@xxxxxxxxxxxxxxxxxxxx: coding style fix]
Link: http://lkml.kernel.org/r/1484238380.15816.42.camel@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>

Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 fs/proc/base.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -3058,6 +3058,8 @@ int proc_pid_readdir(struct file *file,
 	     iter.tgid += 1, iter = next_tgid(ns, iter)) {
 		char name[PROC_NUMBUF];
 		int len;
+
+		cond_resched();
 		if (!has_pid_permissions(ns, iter.task, 2))
 			continue;