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diff --git a/sys/kern/kern_tc.c b/sys/kern/kern_tc.c
--- a/sys/kern/kern_tc.c
+++ b/sys/kern/kern_tc.c
@@ -97,6 +97,10 @@
struct timecounter *timecounter = &dummy_timecounter;
static struct timecounter *timecounters = &dummy_timecounter;
+/* Mutex to protect the timecounter list. */
+static struct mtx tc_lock;
+MTX_SYSINIT(tc_lock, &tc_lock, "tc", MTX_DEF);
+
int tc_min_ticktock_freq = 1;
volatile time_t time_second = 1;
@@ -1188,8 +1192,6 @@
tc->tc_quality);
}
- tc->tc_next = timecounters;
- timecounters = tc;
/*
* Set up sysctl tree for this counter.
*/
@@ -1211,6 +1213,11 @@
SYSCTL_ADD_INT(NULL, SYSCTL_CHILDREN(tc_root), OID_AUTO,
"quality", CTLFLAG_RD, &(tc->tc_quality), 0,
"goodness of time counter");
+
+ mtx_lock(&tc_lock);
+ tc->tc_next = timecounters;
+ timecounters = tc;
+
/*
* Do not automatically switch if the current tc was specifically
* chosen. Never automatically use a timecounter with negative quality.
@@ -1218,22 +1225,24 @@
* worse since this timecounter may not be monotonic.
*/
if (tc_chosen)
- return;
+ goto unlock;
if (tc->tc_quality < 0)
- return;
+ goto unlock;
if (tc_from_tunable[0] != '\0' &&
strcmp(tc->tc_name, tc_from_tunable) == 0) {
tc_chosen = 1;
tc_from_tunable[0] = '\0';
} else {
if (tc->tc_quality < timecounter->tc_quality)
- return;
+ goto unlock;
if (tc->tc_quality == timecounter->tc_quality &&
tc->tc_frequency < timecounter->tc_frequency)
- return;
+ goto unlock;
}
(void)tc->tc_get_timecount(tc);
timecounter = tc;
+unlock:
+ mtx_unlock(&tc_lock);
}
/* Report the frequency of the current timecounter. */
@@ -1479,16 +1488,22 @@
struct timecounter *newtc, *tc;
int error;
+ mtx_lock(&tc_lock);
tc = timecounter;
strlcpy(newname, tc->tc_name, sizeof(newname));
+ mtx_unlock(&tc_lock);
error = sysctl_handle_string(oidp, &newname[0], sizeof(newname), req);
if (error != 0 || req->newptr == NULL)
return (error);
+
+ mtx_lock(&tc_lock);
/* Record that the tc in use now was specifically chosen. */
tc_chosen = 1;
- if (strcmp(newname, tc->tc_name) == 0)
+ if (strcmp(newname, tc->tc_name) == 0) {
+ mtx_unlock(&tc_lock);
return (0);
+ }
for (newtc = timecounters; newtc != NULL; newtc = newtc->tc_next) {
if (strcmp(newname, newtc->tc_name) != 0)
continue;
@@ -1506,11 +1521,11 @@
* use any locking and that it can be called in hard interrupt
* context via 'tc_windup()'.
*/
- return (0);
+ break;
}
- return (EINVAL);
+ mtx_unlock(&tc_lock);
+ return (newtc != NULL ? 0 : EINVAL);
}
-
SYSCTL_PROC(_kern_timecounter, OID_AUTO, hardware,
CTLTYPE_STRING | CTLFLAG_RWTUN | CTLFLAG_NOFETCH | CTLFLAG_MPSAFE, 0, 0,
sysctl_kern_timecounter_hardware, "A",
@@ -1524,12 +1539,17 @@
struct timecounter *tc;
int error;
+ error = sysctl_wire_old_buffer(req, 0);
+ if (error != 0)
+ return (error);
sbuf_new_for_sysctl(&sb, NULL, 0, req);
+ mtx_lock(&tc_lock);
for (tc = timecounters; tc != NULL; tc = tc->tc_next) {
if (tc != timecounters)
sbuf_putc(&sb, ' ');
sbuf_printf(&sb, "%s(%d)", tc->tc_name, tc->tc_quality);
}
+ mtx_unlock(&tc_lock);
error = sbuf_finish(&sb);
sbuf_delete(&sb);
return (error);

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