From: Matthew Dillon <dillon@apollo.backplane.com>
Date: Wed, 23 Oct 2013 01:53:15 +0000 (-0700)
Subject: kernel - Remove debugging kprintf() from procfs
X-Git-Tag: v3.7.0~88
X-Git-Url: https://gitweb.dragonflybsd.org/dragonfly.git/commitdiff_plain/e09db544b831aa5ca10fbacf86387d23c518f067

kernel - Remove debugging kprintf() from procfs

* Remove a procfs console warning that is not longer applicable.  The
  procfs filesystem topology is never quite in sync with reality and
  races between lookups and existing processes are to be expected.
---

diff --git a/sys/vfs/procfs/procfs_vnops.c b/sys/vfs/procfs/procfs_vnops.c
index 5aba1add2a..6e6a6003c4 100644
--- a/sys/vfs/procfs/procfs_vnops.c
+++ b/sys/vfs/procfs/procfs_vnops.c
@@ -1102,15 +1102,20 @@ procfs_readlink(struct vop_readlink_args *ap)
 		len = ksnprintf(buf, sizeof(buf), "%ld", (long)curproc->p_pid);
 
 		return (uiomove(buf, len, ap->a_uio));
-	/*
-	 * There _should_ be no way for an entire process to disappear
-	 * from under us...
-	 */
 	case Pfile:
+		/*
+		 * procfs's directory topology is somewhat asynchronous from
+		 * reality so it is possible for pid requests to race exiting
+		 * processes.  In this situation, bit 31 is set in
+		 * pfs->pfs_pid which guarantees that pfs_pfind() will return
+		 * NULL.
+		 *
+		 * It is also possible to catch a process in the middle of
+		 * an exit sequence so various fields might wind up being
+		 * NULL that are not normally NULL.
+		 */
 		procp = pfs_pfind(pfs->pfs_pid);
 		if (procp == NULL || procp->p_ucred == NULL) {
-			kprintf("procfs_readlink: pid %d disappeared\n",
-			    pfs->pfs_pid);
 			pfs_pdone(procp);
 			return (uiomove("unknown", sizeof("unknown") - 1,
 					ap->a_uio));