Author: mjg
Date: Tue Oct 21 19:05:44 2014
New Revision: 273401
URL: https://svnweb.freebsd.org/changeset/base/273401
Log:
Implement shared locking for sysctl.
Modified:
head/sys/kern/kern_sysctl.c
Modified: head/sys/kern/kern_sysctl.c
==============================================================================
--- head/sys/kern/kern_sysctl.c Tue Oct 21 19:02:26 2014 (r273400)
+++ head/sys/kern/kern_sysctl.c Tue Oct 21 19:05:44 2014 (r273401)
@@ -91,6 +91,10 @@ static struct sx sysctlmemlock;
#define SYSCTL_XLOCK() sx_xlock(&sysctllock)
#define SYSCTL_XUNLOCK() sx_xunlock(&sysctllock)
+#define SYSCTL_SLOCK() sx_slock(&sysctllock)
+#define SYSCTL_SUNLOCK() sx_sunlock(&sysctllock)
+#define SYSCTL_XLOCKED() sx_xlocked(&sysctllock)
+#define SYSCTL_ASSERT_LOCKED() sx_assert(&sysctllock, SA_LOCKED)
#define SYSCTL_ASSERT_XLOCKED() sx_assert(&sysctllock, SA_XLOCKED)
#define SYSCTL_INIT() sx_init(&sysctllock, "sysctl lock")
#define SYSCTL_SLEEP(ch, wmesg, timo)
\
@@ -106,12 +110,35 @@ static int sysctl_remove_oid_locked(stru
static int sysctl_old_kernel(struct sysctl_req *, const void *, size_t);
static int sysctl_new_kernel(struct sysctl_req *, void *, size_t);
+static void
+sysctl_lock(bool xlock)
+{
+
+ if (xlock)
+ SYSCTL_XLOCK();
+ else
+ SYSCTL_SLOCK();
+}
+
+static bool
+sysctl_unlock(void)
+{
+ bool xlocked;
+
+ xlocked = SYSCTL_XLOCKED();
+ if (xlocked)
+ SYSCTL_XUNLOCK();
+ else
+ SYSCTL_SUNLOCK();
+ return (xlocked);
+}
+
static struct sysctl_oid *
sysctl_find_oidname(const char *name, struct sysctl_oid_list *list)
{
struct sysctl_oid *oidp;
- SYSCTL_ASSERT_XLOCKED();
+ SYSCTL_ASSERT_LOCKED();
SLIST_FOREACH(oidp, list, oid_link) {
if (strcmp(oidp->oid_name, name) == 0) {
return (oidp);
@@ -144,9 +171,10 @@ sysctl_root_handler_locked(struct sysctl
struct sysctl_req *req)
{
int error;
+ bool xlocked;
- oid->oid_running++;
- SYSCTL_XUNLOCK();
+ atomic_add_int(&oid->oid_running, 1);
+ xlocked = sysctl_unlock();
if (!(oid->oid_kind & CTLFLAG_MPSAFE))
mtx_lock(&Giant);
@@ -154,9 +182,9 @@ sysctl_root_handler_locked(struct sysctl
if (!(oid->oid_kind & CTLFLAG_MPSAFE))
mtx_unlock(&Giant);
- SYSCTL_XLOCK();
- oid->oid_running--;
- if (oid->oid_running == 0 && (oid->oid_kind & CTLFLAG_DYING) != 0)
+ sysctl_lock(xlocked);
+ if (atomic_fetchadd_int(&oid->oid_running, -1) == 1 &&
+ (oid->oid_kind & CTLFLAG_DYING) != 0)
wakeup(&oid->oid_running);
return (error);
@@ -852,7 +880,7 @@ sysctl_sysctl_next_ls(struct sysctl_oid_
{
struct sysctl_oid *oidp;
- SYSCTL_ASSERT_XLOCKED();
+ SYSCTL_ASSERT_LOCKED();
*len = level;
SLIST_FOREACH(oidp, lsp, oid_link) {
*next = oidp->oid_number;
@@ -939,7 +967,7 @@ name2oid(char *name, int *oid, int *len,
struct sysctl_oid_list *lsp = &sysctl__children;
char *p;
- SYSCTL_ASSERT_XLOCKED();
+ SYSCTL_ASSERT_LOCKED();
for (*len = 0; *len < CTL_MAXNAME;) {
p = strsep(&name, ".");
@@ -1364,9 +1392,9 @@ kernel_sysctl(struct thread *td, int *na
req.newfunc = sysctl_new_kernel;
req.lock = REQ_UNWIRED;
- SYSCTL_XLOCK();
+ SYSCTL_SLOCK();
error = sysctl_root(0, name, namelen, &req);
- SYSCTL_XUNLOCK();
+ SYSCTL_SUNLOCK();
if (req.lock == REQ_WIRED && req.validlen > 0)
vsunlock(req.oldptr, req.validlen);
@@ -1498,7 +1526,7 @@ sysctl_find_oid(int *name, u_int namelen
struct sysctl_oid *oid;
int indx;
- SYSCTL_ASSERT_XLOCKED();
+ SYSCTL_ASSERT_LOCKED();
lsp = &sysctl__children;
indx = 0;
while (indx < CTL_MAXNAME) {
@@ -1545,7 +1573,7 @@ sysctl_root(SYSCTL_HANDLER_ARGS)
struct sysctl_oid *oid;
int error, indx, lvl;
- SYSCTL_ASSERT_XLOCKED();
+ SYSCTL_ASSERT_LOCKED();
error = sysctl_find_oid(arg1, arg2, &oid, &indx, req);
if (error)
@@ -1729,9 +1757,9 @@ userland_sysctl(struct thread *td, int *
for (;;) {
req.oldidx = 0;
req.newidx = 0;
- SYSCTL_XLOCK();
+ SYSCTL_SLOCK();
error = sysctl_root(0, name, namelen, &req);
- SYSCTL_XUNLOCK();
+ SYSCTL_SUNLOCK();
if (error != EAGAIN)
break;
kern_yield(PRI_USER);
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