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SubjectRe: [PATCH] sched: share task comm length value to userspace
On Mon, 5 Sep 2011 13:39:03 -0700
Arjan van de Ven <arjan@infradead.org> wrote:

> On Mon, 05 Sep 2011 23:17:05 +0300
> Vladimir Zapolskiy <vz@mleia.com> wrote:
>
> > but eventually having that value in
> > userspace is really desirable. However in assumption that this value
> > is preserved fixed and won't be changed in reasonable perspective,
> > the presented approach becomes the most evident and simple.
>
> yeah if it would never change, your change would be the most simple.
> but I really don't want to pin that thing down....
>
> >
> > >
> > > If we need to export this, we should export it in /proc or /sys
> > > somewhere as a dynamic value.....
> > >
> > Let's do it in a proper way. What's the common practice to export
> > such limit values? I suppose via /proc/sys/kernel, please correct me,
> > if I'm wrong.
>
> that or /sys/kernel
>
> personally I like /proc/sys/kernel for this kind of thing more, but...
> ... others might disagree.
>

Run this:

#include <sys/prctl.h>
#include <errno.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>

main()
{
char comm[512];
int len;

memset(comm, 0, sizeof(comm));
for (len = 1; len < sizeof(comm) - 1; len++) {
char comm2[512];

comm[len - 1] = 'a';
if (prctl(PR_SET_NAME, (unsigned long)comm, 0, 0, 0) < 0) {
fprintf(stderr, "PR_SET_NAME failed with: %s\n",
strerror(errno));
exit(1);
}
if (prctl(PR_GET_NAME, (unsigned long)comm2, 0, 0, 0) < 0) {
fprintf(stderr, "PR_SET_NAME failed with: %s\n",
strerror(errno));
exit(1);
}
if (strlen(comm2) != len) {
printf("%d\n", len);
break;
}
}
exit(0);
}


once per boot, echoing the result into /etc/sizeof-comm. Sell resulting
package to all vendors ;)




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