7 files changed, 55 insertions, 55 deletions

diff --git a/arch/um/Kconfig b/arch/um/Kconfig
index 64fe8d5c067a..740d8a922e48 100644
--- a/arch/um/Kconfig
+++ b/arch/um/Kconfig
@@ -250,18 +250,6 @@ config KERNEL_STACK_ORDER
           be 1 << order pages.  The default is OK unless you're running Valgrind
           on UML, in which case, set this to 3.
 
-config UML_REAL_TIME_CLOCK
-        bool "Real-time Clock"
-        default y
-        help
-          This option makes UML time deltas match wall clock deltas.  This
-          should normally be enabled.  The exception would be if you are
-          debugging with UML and spend long times with UML stopped at a
-          breakpoint.  In this case, when UML is restarted, it will call the
-          timer enough times to make up for the time spent at the breakpoint.
-          This could result in a noticeable lag.  If this is a problem, then
-          disable this option.
-
 endmenu
 
 source "init/Kconfig"
diff --git a/arch/um/defconfig b/arch/um/defconfig
index 9f105c87fcc4..1cbbe980f106 100644
--- a/arch/um/defconfig
+++ b/arch/um/defconfig
@@ -73,8 +73,8 @@ CONFIG_FLATMEM=y
 CONFIG_FLAT_NODE_MEM_MAP=y
 # CONFIG_SPARSEMEM_STATIC is not set
 CONFIG_SPLIT_PTLOCK_CPUS=4
-# CONFIG_TICK_ONESHOT is not set
-# CONFIG_NO_HZ is not set
+CONFIG_TICK_ONESHOT=y
+CONFIG_NO_HZ=y
 CONFIG_HIGH_RES_TIMERS=y
 CONFIG_LD_SCRIPT_DYN=y
 CONFIG_NET=y
@@ -87,7 +87,6 @@ CONFIG_MAGIC_SYSRQ=y
 CONFIG_NEST_LEVEL=0
 # CONFIG_HIGHMEM is not set
 CONFIG_KERNEL_STACK_ORDER=0
-CONFIG_UML_REAL_TIME_CLOCK=y
 
 #
 # Code maturity level options
diff --git a/arch/um/include/os.h b/arch/um/include/os.h
index a6d80721d3c4..e4f2fe11ba50 100644
--- a/arch/um/include/os.h
+++ b/arch/um/include/os.h
@@ -254,6 +254,7 @@ extern void os_dump_core(void);
 extern int switch_timers(int to_real);
 extern void idle_sleep(int secs);
 extern int set_interval(void);
+extern int timer_one_shot(int ticks);
 extern void disable_timer(void);
 extern void uml_idle_timer(void);
 extern unsigned long long os_nsecs(void);
diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c
index 56d75afedbf7..aef494b6b81a 100644
--- a/arch/um/kernel/process.c
+++ b/arch/um/kernel/process.c
@@ -13,6 +13,7 @@
 #include "linux/ptrace.h"
 #include "linux/random.h"
 #include "linux/sched.h"
+#include "linux/tick.h"
 #include "linux/threads.h"
 #include "asm/pgtable.h"
 #include "asm/uaccess.h"
@@ -244,9 +245,11 @@ void default_idle(void)
                 if (need_resched())
                         schedule();
 
+                tick_nohz_stop_sched_tick();
                 switch_timers(1);
                 idle_sleep(10);
                 switch_timers(0);
+                tick_nohz_restart_sched_tick();
         }
 }
 
diff --git a/arch/um/kernel/time.c b/arch/um/kernel/time.c
index 3cb7135e5c47..2acdc7efb2ac 100644
--- a/arch/um/kernel/time.c
+++ b/arch/um/kernel/time.c
@@ -20,41 +20,12 @@ unsigned long long sched_clock(void)
         return (unsigned long long)jiffies_64 * (1000000000 / HZ);
 }
 
-#ifdef CONFIG_UML_REAL_TIME_CLOCK
-static unsigned long long prev_nsecs[NR_CPUS];
-static long long delta[NR_CPUS];                /* Deviation per interval */
-#endif
-
 void timer_handler(int sig, struct uml_pt_regs *regs)
 {
-        unsigned long long ticks = 0;
         unsigned long flags;
-#ifdef CONFIG_UML_REAL_TIME_CLOCK
-        int c = cpu();
-        if (prev_nsecs[c]) {
-                /* We've had 1 tick */
-                unsigned long long nsecs = os_nsecs();
-
-                delta[c] += nsecs - prev_nsecs[c];
-                prev_nsecs[c] = nsecs;
-
-                /* Protect against the host clock being set backwards */
-                if (delta[c] < 0)
-                        delta[c] = 0;
-
-                ticks += (delta[c] * HZ) / BILLION;
-                delta[c] -= (ticks * BILLION) / HZ;
-        }
-        else prev_nsecs[c] = os_nsecs();
-#else
-        ticks = 1;
-#endif
 
         local_irq_save(flags);
-        while (ticks > 0) {
-                do_IRQ(TIMER_IRQ, regs);
-                ticks--;
-        }
+        do_IRQ(TIMER_IRQ, regs);
         local_irq_restore(flags);
 }
 
@@ -68,10 +39,8 @@ static void itimer_set_mode(enum clock_event_mode mode,
 
         case CLOCK_EVT_MODE_SHUTDOWN:
         case CLOCK_EVT_MODE_UNUSED:
-                disable_timer();
-                break;
         case CLOCK_EVT_MODE_ONESHOT:
-                BUG();
+                disable_timer();
                 break;
 
         case CLOCK_EVT_MODE_RESUME:
@@ -79,13 +48,19 @@ static void itimer_set_mode(enum clock_event_mode mode,
         }
 }
 
+static int itimer_next_event(unsigned long delta,
+                             struct clock_event_device *evt)
+{
+        return timer_one_shot(delta + 1);
+}
+
 static struct clock_event_device itimer_clockevent = {
         .name           = "itimer",
         .rating         = 250,
         .cpumask        = CPU_MASK_ALL,
-        .features       = CLOCK_EVT_FEAT_PERIODIC,
+        .features       = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
         .set_mode       = itimer_set_mode,
-        .set_next_event = NULL,
+        .set_next_event = itimer_next_event,
         .shift          = 32,
         .irq            = 0,
 };
diff --git a/arch/um/os-Linux/skas/process.c b/arch/um/os-Linux/skas/process.c
index 0036164bb0fb..3e64814e888e 100644
--- a/arch/um/os-Linux/skas/process.c
+++ b/arch/um/os-Linux/skas/process.c
@@ -287,10 +287,18 @@ int start_userspace(unsigned long stub_stack)
 
 void userspace(struct uml_pt_regs *regs)
 {
+        struct itimerval timer;
+        unsigned long long nsecs, now;
         int err, status, op, pid = userspace_pid[0];
         /* To prevent races if using_sysemu changes under us.*/
         int local_using_sysemu;
 
+        if (getitimer(ITIMER_VIRTUAL, &timer))
+                printk("Failed to get itimer, errno = %d\n", errno);
+        nsecs = timer.it_value.tv_sec * BILLION +
+                timer.it_value.tv_usec * 1000;
+        nsecs += os_nsecs();
+
         while (1) {
                 restore_registers(pid, regs);
 
@@ -333,8 +341,18 @@ void userspace(struct uml_pt_regs *regs)
                         case SIGTRAP:
                                 relay_signal(SIGTRAP, regs);
                                 break;
-                        case SIGIO:
                         case SIGVTALRM:
+                                now = os_nsecs();
+                                if(now < nsecs)
+                                        break;
+                                block_signals();
+                                (*sig_info[sig])(sig, regs);
+                                unblock_signals();
+                                nsecs = timer.it_value.tv_sec * BILLION +
+                                        timer.it_value.tv_usec * 1000;
+                                nsecs += os_nsecs();
+                                break;
+                        case SIGIO:
                         case SIGILL:
                         case SIGBUS:
                         case SIGFPE:
@@ -378,6 +396,7 @@ __initcall(init_thread_regs);
 
 int copy_context_skas0(unsigned long new_stack, int pid)
 {
+        struct timeval tv = { .tv_sec = 0, .tv_usec = 1000000 / UM_HZ };
         int err;
         unsigned long current_stack = current_stub_stack();
         struct stub_data *data = (struct stub_data *) current_stack;
@@ -392,9 +411,9 @@ int copy_context_skas0(unsigned long new_stack, int pid)
         *data = ((struct stub_data) { .offset   = MMAP_OFFSET(new_offset),
                                       .fd       = new_fd,
                                       .timer    = ((struct itimerval)
-                                                    { { 0, 1000000 / UM_HZ },
-                                                      { 0, 1000000 / UM_HZ }})
-                                 });
+                                                   { .it_value = tv,
+                                                     .it_interval = tv }) });
+
         err = ptrace_setregs(pid, thread_regs);
         if (err < 0)
                 panic("copy_context_skas0 : PTRACE_SETREGS failed, "
diff --git a/arch/um/os-Linux/time.c b/arch/um/os-Linux/time.c
index 6ff3d98281ba..9ffc61ac8ed6 100644
--- a/arch/um/os-Linux/time.c
+++ b/arch/um/os-Linux/time.c
@@ -26,6 +26,21 @@ int set_interval(void)
         return 0;
 }
 
+int timer_one_shot(int ticks)
+{
+        unsigned long usec = ticks * 1000000 / UM_HZ;
+        unsigned long sec = usec / 1000000;
+        struct itimerval interval;
+
+        usec %= 1000000;
+        interval = ((struct itimerval) { { 0, 0 }, { sec, usec } });
+
+        if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
+                return -errno;
+
+        return 0;
+}
+
 void disable_timer(void)
 {
         struct itimerval disable = ((struct itimerval) { { 0, 0 }, { 0, 0 }});
@@ -74,7 +89,7 @@ unsigned long long os_nsecs(void)
         struct timeval tv;
 
         gettimeofday(&tv, NULL);
-        return (unsigned long long) tv.tv_sec * BILLION + tv.tv_usec * 1000;
+        return timeval_to_ns(&tv);
 }
 
 void idle_sleep(int secs)