Add a global sx sigio_lock to protect the pointer to the sigio object

of a socket.  This avoids lock order reversal caused by locking a
process in pgsigio().

sowakeup() and the callers of it (sowwakeup, soisconnected, etc.) now
require sigio_lock to be locked.  Provide sowwakeup_locked(),
soisconnected_locked(), and so on in case where we have to modify a
socket and wake up a process atomically.

1 files changed, 2 insertions, 0 deletions

diff --git a/sys/kern/kern_descrip.c b/sys/kern/kern_descrip.c
index 65f85d5..c645a56 100644
--- a/sys/kern/kern_descrip.c
+++ b/sys/kern/kern_descrip.c
@@ -113,6 +113,7 @@ struct filelist filehead;	/* head of list of open files */
 int nfiles;			/* actual number of open files */
 extern int cmask;	
 struct sx filelist_lock;	/* sx to protect filelist */
+struct sx sigio_lock;		/* sx to protect pointers to sigio */
 
 /*
  * System calls on descriptors.
@@ -2186,4 +2187,5 @@ filelistinit(dummy)
 	    NULL, NULL, UMA_ALIGN_PTR, 0);
 
 	sx_init(&filelist_lock, "filelist lock");
+	sx_init(&sigio_lock, "sigio lock");
 }