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Date:      Thu, 21 May 2009 14:51:32 +0000 (UTC)
From:      John Baldwin <jhb@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-7@freebsd.org
Subject:   svn commit: r192538 - in stable/7/sys: . contrib/pf dev/ath/ath_hal dev/cxgb kern
Message-ID:  <200905211451.n4LEpWDu069827@svn.freebsd.org>
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Author: jhb
Date: Thu May 21 14:51:31 2009
New Revision: 192538
URL: http://svn.freebsd.org/changeset/base/192538

Log:
  MFC: Use a separate sx lock to try to limit wiring too much user memory for
  userland sysctl requests.  "Small" userland requests can now run
  concurrently.

Modified:
  stable/7/sys/   (props changed)
  stable/7/sys/contrib/pf/   (props changed)
  stable/7/sys/dev/ath/ath_hal/   (props changed)
  stable/7/sys/dev/cxgb/   (props changed)
  stable/7/sys/kern/kern_sysctl.c

Modified: stable/7/sys/kern/kern_sysctl.c
==============================================================================
--- stable/7/sys/kern/kern_sysctl.c	Thu May 21 14:43:12 2009	(r192537)
+++ stable/7/sys/kern/kern_sysctl.c	Thu May 21 14:51:31 2009	(r192538)
@@ -76,11 +76,12 @@ static MALLOC_DEFINE(M_SYSCTLTMP, "sysct
  * API rather than using the dynamic API.  Use of the dynamic API is
  * strongly encouraged for most code.
  *
- * This lock is also used to serialize userland sysctl requests.  Some
- * sysctls wire user memory, and serializing the requests limits the
- * amount of wired user memory in use.
+ * The sysctlmemlock is used to limit the amount of user memory wired for
+ * sysctl requests.  This is implemented by serializing any userland
+ * sysctl requests larger than a single page via an exclusive lock.
  */
 static struct sx sysctllock;
+static struct sx sysctlmemlock;
 
 #define	SYSCTL_SLOCK()		sx_slock(&sysctllock)
 #define	SYSCTL_SUNLOCK()	sx_sunlock(&sysctllock)
@@ -542,6 +543,7 @@ sysctl_register_all(void *arg)
 {
 	struct sysctl_oid **oidp;
 
+	sx_init(&sysctlmemlock, "sysctl mem");
 	SYSCTL_INIT();
 	SYSCTL_XLOCK();
 	SET_FOREACH(oidp, sysctl_set)
@@ -1466,7 +1468,7 @@ userland_sysctl(struct thread *td, int *
     size_t *oldlenp, int inkernel, void *new, size_t newlen, size_t *retval,
     int flags)
 {
-	int error = 0;
+	int error = 0, memlocked;
 	struct sysctl_req req;
 
 	bzero(&req, sizeof req);
@@ -1506,13 +1508,19 @@ userland_sysctl(struct thread *td, int *
 	if (KTRPOINT(curthread, KTR_SYSCTL))
 		ktrsysctl(name, namelen);
 #endif
-	
-	SYSCTL_XLOCK();
+
+	if (req.oldlen > PAGE_SIZE) {
+		memlocked = 1;
+		sx_xlock(&sysctlmemlock);
+	} else
+		memlocked = 0;
 
 	for (;;) {
 		req.oldidx = 0;
 		req.newidx = 0;
+		SYSCTL_SLOCK();
 		error = sysctl_root(0, name, namelen, &req);
+		SYSCTL_SUNLOCK();
 		if (error != EAGAIN)
 			break;
 		uio_yield();
@@ -1521,7 +1529,8 @@ userland_sysctl(struct thread *td, int *
 
 	if (req.lock == REQ_WIRED && req.validlen > 0)
 		vsunlock(req.oldptr, req.validlen);
-	SYSCTL_XUNLOCK();
+	if (memlocked)
+		sx_xunlock(&sysctlmemlock);
 
 	if (error && error != ENOMEM)
 		return (error);

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