[PATCH] uml: add locking to xtime accesses

do_timer must be called with xtime_lock held.  I'm not sure boot_timer_handler
needs this, however I don't think it hurts: it simply disables irq and takes a
spinlock.

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 8 insertions, 2 deletions

diff --git a/arch/um/kernel/time_kern.c b/arch/um/kernel/time_kern.c
index 87cdbc560d36..08dd727e79e4 100644
--- a/arch/um/kernel/time_kern.c
+++ b/arch/um/kernel/time_kern.c
@@ -96,11 +96,15 @@ void time_init_kern(void)
 
 void do_boot_timer_handler(struct sigcontext * sc)
 {
+        unsigned long flags;
         struct pt_regs regs;
 
         CHOOSE_MODE((void) (UPT_SC(&regs.regs) = sc),
                     (void) (regs.regs.skas.is_user = 0));
+
+        write_seqlock_irqsave(&xtime_lock, flags);
         do_timer(&regs);
+        write_sequnlock_irqrestore(&xtime_lock, flags);
 }
 
 static DEFINE_SPINLOCK(timer_spinlock);
@@ -125,15 +129,17 @@ irqreturn_t um_timer(int irq, void *dev, struct pt_regs *regs)
         unsigned long long nsecs;
         unsigned long flags;
 
+        write_seqlock_irqsave(&xtime_lock, flags);
+
         do_timer(regs);
 
-        write_seqlock_irqsave(&xtime_lock, flags);
         nsecs = get_time() + local_offset;
         xtime.tv_sec = nsecs / NSEC_PER_SEC;
         xtime.tv_nsec = nsecs - xtime.tv_sec * NSEC_PER_SEC;
+
         write_sequnlock_irqrestore(&xtime_lock, flags);
 
-        return(IRQ_HANDLED);
+        return IRQ_HANDLED;
 }
 
 long um_time(int __user *tloc)