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net: Fix soft lockups/OOM issues w/ unix garbage collector

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This is an implementation of David Miller's suggested fix in:
  https://bugzilla.redhat.com/show_bug.cgi?id=470201

It has been updated to use wait_event() instead of
wait_event_interruptible().

Paraphrasing the description from the above report, it makes sendmsg()
block while UNIX garbage collection is in progress. This avoids a
situation where child processes continue to queue new FDs over a
AF_UNIX socket to a parent which is in the exit path and running
garbage collection on these FDs. This contention can result in soft
lockups and oom-killing of unrelated processes.

Signed-off-by: dann frazier <dannf@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
dann frazier 2008-11-26 15:32:27 -08:00 committed by David S. Miller
parent efbbced361
commit 5f23b73496
3 changed files with 13 additions and 3 deletions
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1
include/net/af_unix.h
View file

@ -9,6 +9,7 @@
extern void unix_inflight(struct file *fp);
extern void unix_notinflight(struct file *fp);
extern void unix_gc(void);
extern void wait_for_unix_gc(void);
#define UNIX_HASH_SIZE 256

2
net/unix/af_unix.c
View file

@ -1343,6 +1343,7 @@ static int unix_dgram_sendmsg(struct kiocb *kiocb, struct socket *sock,
if (NULL == siocb->scm)
siocb->scm = &tmp_scm;
wait_for_unix_gc();
err = scm_send(sock, msg, siocb->scm);
if (err < 0)
return err;
@ -1493,6 +1494,7 @@ static int unix_stream_sendmsg(struct kiocb *kiocb, struct socket *sock,
if (NULL == siocb->scm)
siocb->scm = &tmp_scm;
wait_for_unix_gc();
err = scm_send(sock, msg, siocb->scm);
if (err < 0)
return err;

13
net/unix/garbage.c
View file

@ -80,6 +80,7 @@
#include <linux/file.h>
#include <linux/proc_fs.h>
#include <linux/mutex.h>
#include <linux/wait.h>
#include <net/sock.h>
#include <net/af_unix.h>
@ -91,6 +92,7 @@
static LIST_HEAD(gc_inflight_list);
static LIST_HEAD(gc_candidates);
static DEFINE_SPINLOCK(unix_gc_lock);
static DECLARE_WAIT_QUEUE_HEAD(unix_gc_wait);
unsigned int unix_tot_inflight;
@ -266,12 +268,16 @@ static void inc_inflight_move_tail(struct unix_sock *u)
list_move_tail(&u->link, &gc_candidates);
}
/* The external entry point: unix_gc() */
static bool gc_in_progress = false;
void wait_for_unix_gc(void)
{
wait_event(unix_gc_wait, gc_in_progress == false);
}
/* The external entry point: unix_gc() */
void unix_gc(void)
{
static bool gc_in_progress = false;
struct unix_sock *u;
struct unix_sock *next;
struct sk_buff_head hitlist;
@ -376,6 +382,7 @@ void unix_gc(void)
/* All candidates should have been detached by now. */
BUG_ON(!list_empty(&gc_candidates));
gc_in_progress = false;
wake_up(&unix_gc_wait);
out:
spin_unlock(&unix_gc_lock);