linux-kernel - Re: [PATCH] prevent timespec/timeval to ktime

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Date:	Sat, 02 Sep 2006 21:28:26 +0200
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Andrew Morton <akpm@...l.org>
Cc:	Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>,
	Frank v Waveren <fvw@....cx>
Subject: Re: [PATCH] prevent timespec/timeval to ktime_t overflow

On Sat, 2006-09-02 at 20:41 +0200, Thomas Gleixner wrote:
> This smells like gcc magic. Can you please disassemble the code in
> question ?

Doh. 

Fortunately I own shares of a brown-paperbag-factory and the dividend is
payed in kind.

> > I wonder if this is related to the occasional hrtimr_run_queues() lockup
> > which Andi is encountering.
> 
> Hmm, not sure.

I'm quite sure right now.

	tglx


diff --git a/include/linux/ktime.h b/include/linux/ktime.h
index ed3396d..84eeecd 100644
--- a/include/linux/ktime.h
+++ b/include/linux/ktime.h
@@ -56,7 +56,8 @@ typedef union {
 #endif
 } ktime_t;
 
-#define KTIME_MAX			(~((u64)1 << 63))
+#define KTIME_MAX			((s64)~((u64)1 << 63))
+#define KTIME_SEC_MAX			(KTIME_MAX / NSEC_PER_SEC)
 
 /*
  * ktime_t definitions when using the 64-bit scalar representation:
@@ -73,6 +74,10 @@ typedef union {
  */
 static inline ktime_t ktime_set(const long secs, const unsigned long nsecs)
 {
+#if (BITS_PER_LONG == 64)
+	if (unlikely(secs >= KTIME_SEC_MAX))
+		return (ktime_t){ .tv64 = KTIME_MAX };
+#endif
 	return (ktime_t) { .tv64 = (s64)secs * NSEC_PER_SEC + (s64)nsecs };
 }
 



-- 
VGER BF report: U 0.482714
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