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Message-ID: <8309aff7e55f0c7fe973bb2d1e6b6b3a80ac5a99.1703126594.git.nabijaczleweli@nabijaczleweli.xyz>
Date: Thu, 21 Dec 2023 04:08:51 +0100
From:
Ahelenia Ziemiańska <nabijaczleweli@...ijaczleweli.xyz>
Cc: Jens Axboe <axboe@...nel.dk>, Christian Brauner <brauner@...nel.org>,
Alexander Viro <viro@...iv.linux.org.uk>, linux-fsdevel@...r.kernel.org,
"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
Kuniyuki Iwashima <kuniyu@...zon.com>, David Howells <dhowells@...hat.com>,
Alexander Mikhalitsyn <alexander@...alicyn.com>, John Fastabend <john.fastabend@...il.com>,
Daan De Meyer <daan.j.demeyer@...il.com>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 02/11] af_unix: unix_stream_splice_read: always request
MSG_DONTWAIT
Otherwise we risk sleeping with the pipe locked for indeterminate
lengths of time ‒ given:
cat > unix.c <<^D
#define _GNU_SOURCE
#include <fcntl.h>
#include <sys/socket.h>
#include <sys/un.h>
int main()
{
int sp[2];
socketpair(AF_UNIX, SOCK_STREAM, 0, sp);
for (;;)
splice(sp[0], 0, 1, 0, 128 * 1024 * 1024, 0);
}
^D
cc unix.c -o unix
mkfifo fifo
./unix > fifo &
read -r _ < fifo &
sleep 0.1
echo zupa > fifo
unix used to sleep in splice and the shell used to enter an
uninterruptible sleep in open("fifo");
now the splice returns -EAGAIN and the whole program completes.
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@...ijaczleweli.xyz>
---
net/unix/af_unix.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index ac1f2bc18fc9..bae84552bf58 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -2921,15 +2921,12 @@ static ssize_t unix_stream_splice_read(struct socket *sock, loff_t *ppos,
.pipe = pipe,
.size = size,
.splice_flags = flags,
+ .flags = MSG_DONTWAIT,
};
if (unlikely(*ppos))
return -ESPIPE;
- if (sock->file->f_flags & O_NONBLOCK ||
- flags & SPLICE_F_NONBLOCK)
- state.flags = MSG_DONTWAIT;
-
return unix_stream_read_generic(&state, false);
}
--
2.39.2
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