Commit 3cc4a84e authored Dec 03, 2015 by Eric Dumazet Committed by Al Viro Jan 09, 2016

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>

parent bc51b2a9

fs/proc/fd.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -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();