proc: add a schedule point in proc_pid_readdir()

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@linux-foundation.org: coding style fix]
Link: http://lkml.kernel.org/r/1484238380.15816.42.camel@edumazet-glaptop3.roam.corp.google.com
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 8e7e61b28f31c037961c081d09a7be5f818013ef..87c9a9aacda3601e2686e239243f447728137943 100644 (file)
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -3179,6 +3179,8 @@ int proc_pid_readdir(struct file *file, struct dir_context *ctx)
             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;