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Subject[PATCH] nix RUSAGE_GROUP
After my cleanup of the rusage semantics was so quickly taken in by Andrew
and Linus without comment, I wonder if I should not have tried to be so
accommodating of potential objections as I was. :-)

In my original posting, I solicited comment on whether introducing
RUSAGE_GROUP as distinct from RUSAGE_SELF was warranted. Note that we've
now changed the behavior of the times system call when using CLONE_THREAD,
so changing getrusage RUSAGE_SELF to match would be consistent. I think
that changing the meaning of the old RUSAGE_SELF value is preferable to
introducing the new value for the proper POSIX getrusage behavior. This
patch against Linus's current tree dumps RUSAGE_GROUP and makes RUSAGE_SELF
have the fixed behavior.

If there is interest in having a new explicit interface to sample a single
thread's stats alone, then I think that would be better done by introducing
a new value for RUSAGE_THREAD. This is trivial to implement, but I won't
offer patches bloating the interface if noone is actually interested in
using it.


Thanks,
Roland


Index: linux-2.6.9/include/linux/resource.h
===================================================================
RCS file: /home/roland/redhat/bkcvs/linux-2.5/include/linux/resource.h,v
retrieving revision 1.6
diff -b -B -p -u -r1.6 resource.h
--- linux-2.6.9/include/linux/resource.h 31 Aug 2004 17:35:38 -0000 1.6
+++ linux-2.6.9/include/linux/resource.h 1 Sep 2004 22:20:30 -0000
@@ -17,7 +17,6 @@
#define RUSAGE_SELF 0
#define RUSAGE_CHILDREN (-1)
#define RUSAGE_BOTH (-2) /* sys_wait4() uses this */
-#define RUSAGE_GROUP (-3) /* thread group sum + dead threads */

struct rusage {
struct timeval ru_utime; /* user time used */
Index: linux-2.6.9/kernel/sys.c
===================================================================
RCS file: /home/roland/redhat/bkcvs/linux-2.5/kernel/sys.c,v
retrieving revision 1.88
diff -b -B -p -u -r1.88 sys.c
--- linux-2.6.9/kernel/sys.c 31 Aug 2004 17:35:38 -0000 1.88
+++ linux-2.6.9/kernel/sys.c 1 Sep 2004 22:20:24 -0000
@@ -1565,7 +1565,7 @@ asmlinkage long sys_setrlimit(unsigned i
* This expects to be called with tasklist_lock read-locked or better,
* and the siglock not locked. It may momentarily take the siglock.
*
- * When sampling multiple threads for RUSAGE_GROUP, under SMP we might have
+ * When sampling multiple threads for RUSAGE_SELF, under SMP we might have
* races with threads incrementing their own counters. But since word
* reads are atomic, we either get new values or old values and we don't
* care which for the sums. We always take the siglock to protect reading
@@ -1586,14 +1586,6 @@ void k_getrusage(struct task_struct *p,
return;

switch (who) {
- case RUSAGE_SELF:
- jiffies_to_timeval(p->utime, &r->ru_utime);
- jiffies_to_timeval(p->stime, &r->ru_stime);
- r->ru_nvcsw = p->nvcsw;
- r->ru_nivcsw = p->nivcsw;
- r->ru_minflt = p->min_flt;
- r->ru_majflt = p->maj_flt;
- break;
case RUSAGE_CHILDREN:
spin_lock_irqsave(&p->sighand->siglock, flags);
utime = p->signal->cutime;
@@ -1606,7 +1598,7 @@ void k_getrusage(struct task_struct *p,
jiffies_to_timeval(utime, &r->ru_utime);
jiffies_to_timeval(stime, &r->ru_stime);
break;
- case RUSAGE_GROUP:
+ case RUSAGE_SELF:
spin_lock_irqsave(&p->sighand->siglock, flags);
utime = stime = 0;
goto sum_group;
@@ -1655,8 +1647,7 @@ int getrusage(struct task_struct *p, int

asmlinkage long sys_getrusage(int who, struct rusage __user *ru)
{
- if (who != RUSAGE_SELF && who != RUSAGE_CHILDREN
- && who != RUSAGE_GROUP)
+ if (who != RUSAGE_SELF && who != RUSAGE_CHILDREN)
return -EINVAL;
return getrusage(current, who, ru);
}
-
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