From: Eric Dumazet <edumazet@google.com>
Date: Thu, 3 Dec 2015 19:12:07 +0000 (-0800)
Subject: proc: add a reschedule point in proc_readfd_common()
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=3cc4a84e026e8d61b7ffe4a7367ed09a555f2c5b;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git

proc: add a reschedule point in proc_readfd_common()

User can pass an arbitrary large buffer to getdents().

It is typically a 32KB buffer used by libc scandir() implementation.

When scanning /proc/{pid}/fd, we can hold cpu way too long,
so add a cond_resched() to be kind with other tasks.

We've seen latencies of more than 50ms on real workloads.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---

diff --git a/fs/proc/fd.c b/fs/proc/fd.c
index 3c2a915c695a..56afa5ef08f2 100644
--- a/fs/proc/fd.c
+++ b/fs/proc/fd.c
@@ -258,6 +258,7 @@ static int proc_readfd_common(struct file *file, struct dir_context *ctx,
 				     name, len, instantiate, p,
 				     (void *)(unsigned long)fd))
 			goto out_fd_loop;
+		cond_resched();
 		rcu_read_lock();
 	}
 	rcu_read_unlock();