Re: PR/53998 CVS commit: src/sys/kern

[christos%zoulas.com@localhost (Christos Zoulas)]

On Feb 24,  5:20pm, joel.bertrand%systella.fr@localhost (=?UTF-8?Q?BERTRAND_Jo=c3=abl?=) wrote:
-- Subject: Re: PR/53998 CVS commit: src/sys/kern

I can see the race conditions for p_nsems, but since this intended just
to be a guard to prevent abuse, it is simple enough to avoid it for now...

christos

Index: uipc_sem.c
===================================================================
RCS file: /cvsroot/src/sys/kern/uipc_sem.c,v
retrieving revision 1.54
diff -u -p -u -r1.54 uipc_sem.c
--- uipc_sem.c	21 Feb 2019 21:49:23 -0000	1.54
+++ uipc_sem.c	24 Feb 2019 20:25:43 -0000
@@ -511,7 +511,11 @@ ksem_free(ksem_t *ks)
 	kmem_free(ks, sizeof(ksem_t));
 
 	atomic_dec_uint(&nsems_total);
- 	atomic_dec_uint(&curproc->p_nsems);	
+ 	while ((int)atomic_dec_uint_nv(&curproc->p_nsems) < 0) {
+		printf("%s: pid=%d sem=%p negarive refcount %u\n", __func__,
+		    curproc->p_pid, ks, curproc->p_nsems);
+		atomic_inc_uint(&curproc->p_nsems);
+	}
 }
 
 #define	KSEM_ID_IS_PSHARED(id)		\