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>

1 files changed, 3 insertions, 6 deletions

diff --git a/arch/um/os-Linux/signal.c b/arch/um/os-Linux/signal.c
index 49c113b576b7..1c5267ec13b0 100644
--- 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);