uml: fix timer switching

Fix up the switching between virtual and real timers.  The idle loop sleeps,
so the timer at that point must be real time.  At all other times, the timer
must be virtual.  Even when userspace is running, and the kernel is asleep,
the virtual timer is correct because the process timer will be running and the
process timer will be firing.

The timer switch used to be in the context switch and timer handler code.
This is moved to the idle loop and the signal handler, making it much more
clear why it is happening.

switch_timers now returns the old timer type so that it may be restored.  The
signal handler uses this in order to restore the previous timer type when it
returns.

Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/um/include/os.h b/arch/um/include/os.h
index e861c8adb44faddb9d83131ceabe61b006cd0817..12de1ea683705e2c26131552569380815a2a728b 100644 (file)
--- a/arch/um/include/os.h
+++ b/arch/um/include/os.h
@@ -250,7 +250,7 @@ extern void os_dump_core(void);
 /* time.c */
 #define BILLION (1000 * 1000 * 1000)
 
-extern void switch_timers(int to_real);
+extern int switch_timers(int to_real);
 extern void idle_sleep(int secs);
 extern int set_interval(int is_virtual);
 extern void disable_timer(void);

diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c
index 8a6882dfba01daad16a3598a76a921e4cf1ad304..56d75afedbf7de3bd2d26c6f81b9500a4a099593 100644 (file)
--- a/arch/um/kernel/process.c
+++ b/arch/um/kernel/process.c
@@ -95,18 +95,11 @@ void *_switch_to(void *prev, void *next, void *last)
        do {
                current->thread.saved_task = NULL;
 
-               /* XXX need to check runqueues[cpu].idle */
-               if (current->pid == 0)
-                       switch_timers(0);
-
                switch_threads(&from->thread.switch_buf,
                               &to->thread.switch_buf);
 
                arch_switch_to(current->thread.prev_sched, current);
 
-               if (current->pid == 0)
-                       switch_timers(1);
-
                if (current->thread.saved_task)
                        show_regs(&(current->thread.regs));
                next= current->thread.saved_task;
@@ -251,7 +244,9 @@ void default_idle(void)
                if (need_resched())
                        schedule();
 
+               switch_timers(1);
                idle_sleep(10);
+               switch_timers(0);
        }
 }
 

diff --git a/arch/um/os-Linux/signal.c b/arch/um/os-Linux/signal.c
index 49c113b576b7695954585e7c85c3be0fd3c1f35e..1c5267ec13b0943e324f32528b1eb5d77405af2d 100644 (file)
--- a/arch/um/os-Linux/signal.c
+++ b/arch/um/os-Linux/signal.c
@@ -59,17 +59,11 @@ static void real_alarm_handler(int sig, struct sigcontext *sc)
 {
        struct uml_pt_regs regs;
 
-       if (sig == SIGALRM)
-               switch_timers(0);
-
        if (sc != NULL)
                copy_sc(&regs, sc);
        regs.is_user = 0;
        unblock_signals();
        timer_handler(sig, &regs);
-
-       if (sig == SIGALRM)
-               switch_timers(1);
 }
 
 void alarm_handler(int sig, struct sigcontext *sc)
@@ -116,6 +110,7 @@ void (*handlers[_NSIG])(int sig, struct sigcontext *sc);
 void handle_signal(int sig, struct sigcontext *sc)
 {
        unsigned long pending = 1UL << sig;
+       int timer = switch_timers(0);
 
        do {
                int nested, bail;
@@ -152,6 +147,8 @@ void handle_signal(int sig, struct sigcontext *sc)
                if (!nested)
                        pending = from_irq_stack(nested);
        } while (pending);
+
+       switch_timers(timer);
 }
 
 extern void hard_handler(int sig);

diff --git a/arch/um/os-Linux/time.c b/arch/um/os-Linux/time.c
index 5939653f99eab45d6a193ab396ffebe53d5a3d4a..a16a0f484edc8f3fa517c7e2d8a479ef6f2624c3 100644 (file)
--- a/arch/um/os-Linux/time.c
+++ b/arch/um/os-Linux/time.c
@@ -12,6 +12,8 @@
 #include "os.h"
 #include "user.h"
 
+static int is_real_timer = 0;
+
 int set_interval(int is_virtual)
 {
        int usec = 1000000/UM_HZ;
@@ -39,12 +41,14 @@ void disable_timer(void)
        signal(SIGVTALRM, SIG_IGN);
 }
 
-void switch_timers(int to_real)
+int switch_timers(int to_real)
 {
        struct itimerval disable = ((struct itimerval) { { 0, 0 }, { 0, 0 }});
-       struct itimerval enable = ((struct itimerval) { { 0, 1000000/UM_HZ },
-                                                       { 0, 1000000/UM_HZ }});
-       int old, new;
+       struct itimerval enable;
+       int old, new, old_type = is_real_timer;
+
+       if(to_real == old_type)
+               return to_real;
 
        if (to_real) {
                old = ITIMER_VIRTUAL;
@@ -55,10 +59,19 @@ void switch_timers(int to_real)
                new = ITIMER_VIRTUAL;
        }
 
-       if ((setitimer(old, &disable, NULL) < 0) ||
-           (setitimer(new, &enable, NULL)))
-               printk(UM_KERN_ERR "switch_timers - setitimer failed, "
+       if (setitimer(old, &disable, &enable) < 0)
+               printk(UM_KERN_ERR "switch_timers - setitimer disable failed, "
+                      "errno = %d\n", errno);
+
+       if((enable.it_value.tv_sec == 0) && (enable.it_value.tv_usec == 0))
+               enable.it_value = enable.it_interval;
+
+       if (setitimer(new, &enable, NULL))
+               printk(UM_KERN_ERR "switch_timers - setitimer enable failed, "
                       "errno = %d\n", errno);
+
+       is_real_timer = to_real;
+       return old_type;
 }
 
 unsigned long long os_nsecs(void)