Dear Linus,
since nobody commented on my last post, I think the 64 bit jiffies patch
seems to be mature enough for submission now.
I assume you still prefer the chunks in seperate mails, this way also my
Bitkeeper stats will look better ;-)
OK, here comes the basic chunk:
Provide a 64 bit jiffies value, updating the high 32 bits with a timer
on 32 bit platforms. Details are encapsulated in the get_jiffies64() call.
Credit for the idea for this lock-free version is due to Albert Cahalan.
Tim
--- linux-2.5.15/include/linux/sched.h Thu May 9 17:47:15 2002
+++ linux-2.5.15-j64/include/linux/sched.h Thu May 9 17:48:20 2002
@@ -460,6 +460,18 @@
#include <asm/current.h>
extern unsigned long volatile jiffies;
+#if BITS_PER_LONG < 48
+#define NEEDS_JIFFIES64
+ extern u64 get_jiffies64(void);
+#else
+ /* jiffies is wide enough to not wrap for 8716 years at HZ==1024 */
+ static inline u64 get_jiffies64(void)
+ {
+ return (u64)jiffies;
+ }
+#endif
+
+
extern unsigned long itimer_ticks;
extern unsigned long itimer_next;
extern void do_timer(struct pt_regs *);
--- linux-2.5.15/kernel/timer.c Mon Mar 18 21:37:09 2002
+++ linux-2.5.15-j64/kernel/timer.c Thu May 9 17:48:20 2002
@@ -68,6 +68,9 @@
extern int do_setitimer(int, struct itimerval *, struct itimerval *);
unsigned long volatile jiffies;
+#ifdef NEEDS_JIFFIES64
+static unsigned int volatile jiffies_msb_flips;
+#endif
unsigned int * prof_buffer;
unsigned long prof_len;
@@ -105,6 +108,8 @@
#define NOOF_TVECS (sizeof(tvecs) / sizeof(tvecs[0]))
+static inline void init_jiffieswrap_timer(void);
+
void init_timervecs (void)
{
int i;
@@ -117,6 +122,8 @@
}
for (i = 0; i < TVR_SIZE; i++)
INIT_LIST_HEAD(tv1.vec + i);
+
+ init_jiffieswrap_timer();
}
static unsigned long timer_jiffies;
@@ -674,6 +681,60 @@
if (TQ_ACTIVE(tq_timer))
mark_bh(TQUEUE_BH);
}
+
+
+#ifdef NEEDS_JIFFIES64
+
+u64 get_jiffies64(void)
+{
+ unsigned long j;
+ unsigned int f;
+
+ f = jiffies_msb_flips; /* avoid races */
+ rmb();
+ j = jiffies;
+
+ /* account for not yet detected flips */
+ f += (f ^ (j>>(BITS_PER_LONG-1))) & 1;
+ return ((u64) f << (BITS_PER_LONG-1)) | j;
+}
+
+/*
+ * Use a timer to periodically check for jiffies wraparounds.
+ * Instead of overflows we count flips of the highest bit so
+ * that we can easily check whether the latest flip is already
+ * accounted for.
+ * Not racy as invocations are several days apart in time and
+ * jiffies_flips is not modified elsewhere.
+ */
+
+static struct timer_list jiffieswrap_timer;
+#define CHECK_JIFFIESWRAP_INTERVAL (1ul << (BITS_PER_LONG-2))
+
+static void check_jiffieswrap(unsigned long data)
+{
+ mod_timer(&jiffieswrap_timer, jiffies + CHECK_JIFFIESWRAP_INTERVAL);
+
+ jiffies_msb_flips += 1 & (jiffies_msb_flips
+ ^ (jiffies>>(BITS_PER_LONG-1)));
+}
+
+static inline void init_jiffieswrap_timer(void)
+{
+ init_timer(&jiffieswrap_timer);
+ jiffieswrap_timer.expires = jiffies + CHECK_JIFFIESWRAP_INTERVAL;
+ jiffieswrap_timer.function = check_jiffieswrap;
+ add_timer(&jiffieswrap_timer);
+}
+
+#else
+
+static inline void init_jiffieswrap_timer(void)
+{
+}
+
+#endif /* NEEDS_JIFFIES64 */
+
#if !defined(__alpha__) && !defined(__ia64__)
-
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This archive was generated by hypermail 2b29 : Tue May 14 2002 - 12:00:16 EST