Stop updating the struct vdso_timehands from even handler executed in

the scheduled task from tc_windup(). Do it directly from tc_windup in
interrupt context [1].

Establish the permanent mapping of the shared page into the kernel
address space, avoiding the potential need to sleep waiting for
allocation of sf buffer during vdso_timehands update. As a
consequence, shared_page_write_start() and shared_page_write_end()
functions are not needed anymore.

Guess and memorize the pointers to native host and compat32 sysentvec
during initialization, to avoid the need to get shared_page_alloc_sx
lock during the update.

In tc_fill_vdso_timehands(), do not loop waiting for timehands
generation to stabilize, since vdso_timehands is written in the same
interrupt context which wrote timehands.

Requested by:	  mav [1]
MFC after:	  29 days

1 files changed, 21 insertions, 41 deletions

diff --git a/sys/kern/kern_tc.c b/sys/kern/kern_tc.c
index 0b8fefe..4a75af5 100644
--- a/sys/kern/kern_tc.c
+++ b/sys/kern/kern_tc.c
@@ -31,7 +31,6 @@ __FBSDID("$FreeBSD$");
 #include <sys/systm.h>
 #include <sys/timeffc.h>
 #include <sys/timepps.h>
-#include <sys/taskqueue.h>
 #include <sys/timetc.h>
 #include <sys/timex.h>
 #include <sys/vdso.h>
@@ -121,12 +120,8 @@ SYSCTL_INT(_kern_timecounter, OID_AUTO, stepwarnings, CTLFLAG_RW,
     &timestepwarnings, 0, "Log time steps");
 
 static void tc_windup(void);
-static void tc_windup_push_vdso(void *ctx, int pending);
 static void cpu_tick_calibrate(int);
 
-static struct task tc_windup_push_vdso_task = TASK_INITIALIZER(0,
-    tc_windup_push_vdso,  0);
-
 static int
 sysctl_kern_boottime(SYSCTL_HANDLER_ARGS)
 {
@@ -1367,7 +1362,7 @@ tc_windup(void)
 #endif
 
 	timehands = th;
-	taskqueue_enqueue_fast(taskqueue_fast, &tc_windup_push_vdso_task);
+	timekeep_push_vdso();
 }
 
 /* Report or change the active timecounter hardware. */
@@ -1394,7 +1389,7 @@ sysctl_kern_timecounter_hardware(SYSCTL_HANDLER_ARGS)
 		(void)newtc->tc_get_timecount(newtc);
 
 		timecounter = newtc;
-		EVENTHANDLER_INVOKE(tc_windup);
+		timekeep_push_vdso();
 		return (0);
 	}
 	return (EINVAL);
@@ -1865,7 +1860,7 @@ sysctl_fast_gettime(SYSCTL_HANDLER_ARGS)
 	if (error != 0)
 		return (error);
 	vdso_th_enable = old_vdso_th_enable;
-	EVENTHANDLER_INVOKE(tc_windup);
+	timekeep_push_vdso();
 	return (0);
 }
 SYSCTL_PROC(_kern_timecounter, OID_AUTO, fast_gettime,
@@ -1877,19 +1872,15 @@ tc_fill_vdso_timehands(struct vdso_timehands *vdso_th)
 {
 	struct timehands *th;
 	uint32_t enabled;
-	int gen;
 
-	do {
-		th = timehands;
-		gen = th->th_generation;
-		vdso_th->th_algo = VDSO_TH_ALGO_1;
-		vdso_th->th_scale = th->th_scale;
-		vdso_th->th_offset_count = th->th_offset_count;
-		vdso_th->th_counter_mask = th->th_counter->tc_counter_mask;
-		vdso_th->th_offset = th->th_offset;
-		vdso_th->th_boottime = boottimebin;
-		enabled = cpu_fill_vdso_timehands(vdso_th);
-	} while (gen == 0 || timehands->th_generation != gen);
+	th = timehands;
+	vdso_th->th_algo = VDSO_TH_ALGO_1;
+	vdso_th->th_scale = th->th_scale;
+	vdso_th->th_offset_count = th->th_offset_count;
+	vdso_th->th_counter_mask = th->th_counter->tc_counter_mask;
+	vdso_th->th_offset = th->th_offset;
+	vdso_th->th_boottime = boottimebin;
+	enabled = cpu_fill_vdso_timehands(vdso_th);
 	if (!vdso_th_enable)
 		enabled = 0;
 	return (enabled);
@@ -1901,30 +1892,19 @@ tc_fill_vdso_timehands32(struct vdso_timehands32 *vdso_th32)
 {
 	struct timehands *th;
 	uint32_t enabled;
-	int gen;
 
-	do {
-		th = timehands;
-		gen = th->th_generation;
-		vdso_th32->th_algo = VDSO_TH_ALGO_1;
-		*(uint64_t *)&vdso_th32->th_scale[0] = th->th_scale;
-		vdso_th32->th_offset_count = th->th_offset_count;
-		vdso_th32->th_counter_mask = th->th_counter->tc_counter_mask;
-		vdso_th32->th_offset.sec = th->th_offset.sec;
-		*(uint64_t *)&vdso_th32->th_offset.frac[0] = th->th_offset.frac;
-		vdso_th32->th_boottime.sec = boottimebin.sec;
-		*(uint64_t *)&vdso_th32->th_boottime.frac[0] = boottimebin.frac;
-		enabled = cpu_fill_vdso_timehands32(vdso_th32);
-	} while (gen == 0 || timehands->th_generation != gen);
+	th = timehands;
+	vdso_th32->th_algo = VDSO_TH_ALGO_1;
+	*(uint64_t *)&vdso_th32->th_scale[0] = th->th_scale;
+	vdso_th32->th_offset_count = th->th_offset_count;
+	vdso_th32->th_counter_mask = th->th_counter->tc_counter_mask;
+	vdso_th32->th_offset.sec = th->th_offset.sec;
+	*(uint64_t *)&vdso_th32->th_offset.frac[0] = th->th_offset.frac;
+	vdso_th32->th_boottime.sec = boottimebin.sec;
+	*(uint64_t *)&vdso_th32->th_boottime.frac[0] = boottimebin.frac;
+	enabled = cpu_fill_vdso_timehands32(vdso_th32);
 	if (!vdso_th_enable)
 		enabled = 0;
 	return (enabled);
 }
 #endif
-
-static void
-tc_windup_push_vdso(void *ctx, int pending)
-{
-
-	EVENTHANDLER_INVOKE(tc_windup);
-}