svn commit: r287362 - head/sys/kern

[Konstantin Belousov]

Author: kib
Date: Tue Sep  1 13:21:32 2015
New Revision: 287362
URL: https://svnweb.freebsd.org/changeset/base/287362

Log:
  Clean up the kqueue use of the uma KPI.
  
  Explain why it is fine to not check for M_NOWAIT failures in
  kqueue_register().  Remove unneeded check for NULL result from
  waitable allocation in kqueue_scan().  uma_free(9) handles NULL
  argument correctly, remove checks for NULL.  Remove useless cast and
  adjust style in knote_alloc().
  
  Sponsored by:	The FreeBSD Foundation
  MFC after:	2 weeks

Modified:
  head/sys/kern/kern_event.c

Modified: head/sys/kern/kern_event.c
==============================================================================
--- head/sys/kern/kern_event.c	Tue Sep  1 13:07:27 2015	(r287361)
+++ head/sys/kern/kern_event.c	Tue Sep  1 13:21:32 2015	(r287362)
@@ -1105,10 +1105,16 @@ kqueue_register(struct kqueue *kq, struc
 	if (fops == NULL)
 		return EINVAL;
 
-	if (kev->flags & EV_ADD)
-		tkn = knote_alloc(waitok);	/* prevent waiting with locks */
-	else
+	if (kev->flags & EV_ADD) {
+		/*
+		 * Prevent waiting with locks.  Non-sleepable
+		 * allocation failures are handled in the loop, only
+		 * if the spare knote appears to be actually required.
+		 */
+		tkn = knote_alloc(waitok);
+	} else {
 		tkn = NULL;
+	}
 
 findkn:
 	if (fops->f_isfd) {
@@ -1310,8 +1316,7 @@ done:
 		FILEDESC_XUNLOCK(td->td_proc->p_fd);
 	if (fp != NULL)
 		fdrop(fp, td);
-	if (tkn != NULL)
-		knote_free(tkn);
+	knote_free(tkn);
 	if (fops != NULL)
 		kqueue_fo_release(filt);
 	return (error);
@@ -1507,10 +1512,6 @@ kqueue_scan(struct kqueue *kq, int maxev
 	} else
 		asbt = 0;
 	marker = knote_alloc(1);
-	if (marker == NULL) {
-		error = ENOMEM;
-		goto done_nl;
-	}
 	marker->kn_status = KN_MARKER;
 	KQ_LOCK(kq);
 
@@ -2385,15 +2386,16 @@ SYSINIT(knote, SI_SUB_PSEUDO, SI_ORDER_A
 static struct knote *
 knote_alloc(int waitok)
 {
-	return ((struct knote *)uma_zalloc(knote_zone,
-	    (waitok ? M_WAITOK : M_NOWAIT)|M_ZERO));
+
+	return (uma_zalloc(knote_zone, (waitok ? M_WAITOK : M_NOWAIT) |
+	    M_ZERO));
 }
 
 static void
 knote_free(struct knote *kn)
 {
-	if (kn != NULL)
-		uma_zfree(knote_zone, kn);
+
+	uma_zfree(knote_zone, kn);
 }
 
 /*