From: Carsten Emde <C.Emde@osadl.org>
To: util-linux@vger.kernel.org
Cc: Carsten Emde <C.Emde@osadl.org>
Subject: [PATCH 1/1] Taskset: check first whether affinity is settable
Date: Fri, 05 Aug 2022 17:48:21 +0200 [thread overview]
Message-ID: <20220805154900.261920576@osadl.org> (raw)
In-Reply-To: 20220805154820.407972387@osadl.org
If the PF_NO_SETAFFINITY process flag is set, the user may not
know why the affinity is not settable. Write a respective message
and do not attempt to set the affinity of this process.
Signed-off-by: Carsten Emde <C.Emde@osadl.org>
---
schedutils/taskset.c | 34 ++++++++++++++++++++++++++++++++++
1 file changed, 34 insertions(+)
Index: util-linux/schedutils/taskset.c
===================================================================
--- util-linux.orig/schedutils/taskset.c
+++ util-linux/schedutils/taskset.c
@@ -35,6 +35,11 @@
#include "c.h"
#include "closestream.h"
+#ifndef PF_NO_SETAFFINITY
+#define PF_NO_SETAFFINITY 0x04000000
+#endif
+#define PF_NO_SETAFFINITY_FLAG 9
+
struct taskset {
pid_t pid; /* task PID */
cpu_set_t *set; /* task CPU mask */
@@ -114,6 +119,8 @@ static void __attribute__((__noreturn__)
static void do_taskset(struct taskset *ts, size_t setsize, cpu_set_t *set)
{
+ char statfilename[32];
+
/* read the current mask */
if (ts->pid) {
if (sched_getaffinity(ts->pid, ts->setsize, ts->set) < 0)
@@ -124,6 +131,33 @@ static void do_taskset(struct taskset *t
if (ts->get_only)
return;
+ /* check whether settable */
+ if (snprintf(statfilename, sizeof(statfilename), "/proc/%d/stat", ts->pid) > 0) {
+ int statfd;
+
+ if ((statfd = open(statfilename, S_IREAD)) > 0) {
+ char stat[1024];
+
+ if (read(statfd, stat, sizeof(stat)) > 0) {
+ char *endptr, *token = strtok(stat, " ");
+ int flags, flagno = PF_NO_SETAFFINITY_FLAG;
+
+ while (token && --flagno > 0)
+ token = strtok(NULL, " ");
+ if (flagno == 0 && *token != '\0') {
+ flags = strtol(token, &endptr, 10);
+ if (endptr == token + strlen(token)) {
+ if (flags & PF_NO_SETAFFINITY) {
+ fputs("warning: affinity cannot be set due to PF_NO_SETAFFINITY flag set\n", stderr);
+ errno = EINVAL;
+ err_affinity(ts->pid, 1);
+ }
+ }
+ }
+ }
+ }
+ }
+
/* set new mask */
if (sched_setaffinity(ts->pid, setsize, set) < 0)
err_affinity(ts->pid, 1);
prev parent reply other threads:[~2022-08-05 15:57 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-05 15:48 [PATCH 0/1] Taskset: check first whether affinity is settable Carsten Emde
2022-08-05 15:48 ` Carsten Emde [this message]
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