linux-kernel - [patch] make siginfo_t si_utime + si_sstime report times in USER

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Message-ID: <cfd18e0f0806250749od875635r9e533d9f834bd8c4@mail.gmail.com>
Date:	Wed, 25 Jun 2008 16:49:33 +0200
From:	"Michael Kerrisk" <mtk.manpages@...glemail.com>
To:	"Thomas Gleixner" <tglx@...utronix.de>,
	"Oleg Nesterov" <oleg@...sign.ru>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Bart Van Assche" <bart.vanassche@...il.com>
Subject: [patch] make siginfo_t si_utime + si_sstime report times in USER_HZ, not HZ

Oleg, Thomas,

In the switch to configurable HZ in 2.6, the treatment of the si_utime
and si_stime fields that are exposed to userland via the siginfo
structure looks to have been botched.  As things stand, these fields
report times in units of HZ, so that userland gets information that
varies depending on the HZ that the kernel was configured with.  This
(trivial, untested) patch changes the reported values to use USER_HZ
units.  What do you think of making this change?

Signed-off-by: Michael Kerrisk <mtk.manpages@...il.com>

--- /home/mtk/ARCHIVE/KERNEL/linux-2.6.26-rc7/kernel/signal.c.orig	2008-06-24
16:20:39.000000000 +0200
+++ /home/mtk/ARCHIVE/KERNEL/linux-2.6.26-rc7/kernel/signal.c	2008-06-24
16:22:17.000000000 +0200
@@ -1379,10 +1379,9 @@

 	info.si_uid = tsk->uid;

-	/* FIXME: find out whether or not this is supposed to be c*time. */
-	info.si_utime = cputime_to_jiffies(cputime_add(tsk->utime,
+	info.si_utime = cputime_to_clock_t(cputime_add(tsk->utime,
 						       tsk->signal->utime));
-	info.si_stime = cputime_to_jiffies(cputime_add(tsk->stime,
+	info.si_stime = cputime_to_clock_t(cputime_add(tsk->stime,
 						       tsk->signal->stime));

 	info.si_status = tsk->exit_code & 0x7f;
@@ -1450,9 +1449,8 @@

 	info.si_uid = tsk->uid;

-	/* FIXME: find out whether or not this is supposed to be c*time. */
-	info.si_utime = cputime_to_jiffies(tsk->utime);
-	info.si_stime = cputime_to_jiffies(tsk->stime);
+	info.si_utime = cputime_to_clock_t(tsk->utime);
+	info.si_stime = cputime_to_clock_t(tsk->stime);

  	info.si_code = why;
  	switch (why) {
--
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