kern/timer: make timer time reads non atomic

This makes such accesses on 32-bits processor without 64-bits atomic
instruction too cumbersome for what it's worth.

3 files changed, 11 insertions, 14 deletions

diff --git a/kern/timer.c b/kern/timer.c
index ba148d5f..77a6bb36 100644
--- a/kern/timer.c
+++ b/kern/timer.c
@@ -239,7 +239,7 @@ timer_set_canceled(struct timer *timer)
 static void
 timer_set_time(struct timer *timer, uint64_t ticks)
 {
-    atomic_store(&timer->ticks, ticks, ATOMIC_RELAXED);
+    timer->ticks = ticks;
 }
 
 static bool
diff --git a/kern/timer.h b/kern/timer.h
index a082c538..ddace45e 100644
--- a/kern/timer.h
+++ b/kern/timer.h
@@ -23,7 +23,6 @@
 
 #include <stdint.h>
 
-#include <kern/atomic.h>
 #include <kern/init.h>
 
 /*
@@ -44,11 +43,14 @@ typedef void (*timer_fn_t)(struct timer *);
 
 /*
  * Return the absolute expiration time of the timer, in ticks.
+ *
+ * This function may not be called while another thread is scheduling the
+ * timer.
  */
 static inline uint64_t
 timer_get_time(const struct timer *timer)
 {
-    return atomic_load(&timer->ticks, ATOMIC_RELAXED);
+    return timer->ticks;
 }
 
 /*
diff --git a/kern/timer_i.h b/kern/timer_i.h
index 40e97f1b..bbe07f9b 100644
--- a/kern/timer_i.h
+++ b/kern/timer_i.h
@@ -29,12 +29,7 @@
  * (c) cpu_data
  * (a) atomic
  *
- * (*) The ticks member represents the expiration date. It may be read without
- * locking the timer, in which case it must be accessed atomically. It
- * may only be updated when the timer is locked though, so reads at such
- * times don't need to be atomic.
- *
- * (**) The cpu member is used to determine which lock serializes access to
+ * (*) The cpu member is used to determine which lock serializes access to
  * the structure. It must be accessed atomically, but updated while the
  * timer is locked.
  */
@@ -44,12 +39,12 @@ struct timer {
         struct work work;
     };
 
-    uint64_t ticks;             /* (c,a,*)  */
+    uint64_t ticks;             /* (c)     */
     timer_fn_t fn;
-    unsigned int cpu;           /* (c,a,**) */
-    unsigned short state;       /* (c)      */
-    unsigned short flags;       /* (c)      */
-    struct thread *joiner;      /* (c)      */
+    unsigned int cpu;           /* (c,a,*) */
+    unsigned short state;       /* (c)     */
+    unsigned short flags;       /* (c)     */
+    struct thread *joiner;      /* (c)     */
 };
 
 #endif /* _KERN_TIMER_I_H */