net: Fix soft lockups/OOM issues w/ unix garbage collector
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>
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index eb90f77..66d5ac4 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1343,6 +1343,7 @@
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 @@
if (NULL == siocb->scm)
siocb->scm = &tmp_scm;
+ wait_for_unix_gc();
err = scm_send(sock, msg, siocb->scm);
if (err < 0)
return err;
diff --git a/net/unix/garbage.c b/net/unix/garbage.c
index 6d4a9a8..abb3ab3 100644
--- a/net/unix/garbage.c
+++ b/net/unix/garbage.c
@@ -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 @@
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 @@
/* 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);
