From: Karel Zak <kzak@redhat.com>
Date: Thu, 11 Aug 2022 08:59:40 +0000 (+0200)
Subject: taskset: warn if affinity is not settable
X-Git-Tag: v2.39-rc1~556
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=adc72421f4db93bc9cd932bac2b0be8197a1d64f;p=thirdparty%2Futil-linux.git

taskset: warn if affinity is not settable

Let's read /proc/#/stat to get process flags and print warning
if the affinity is not settable.

Based on patch from Carsten.

Tested-by: Carsten Emde <C.Emde@osadl.org>
Signed-off-by: Karel Zak <kzak@redhat.com>
---

diff --git a/schedutils/taskset.c b/schedutils/taskset.c
index 0ab7d12e20..0872aa273a 100644
--- a/schedutils/taskset.c
+++ b/schedutils/taskset.c
@@ -35,6 +35,10 @@
 #include "c.h"
 #include "closestream.h"
 
+#ifndef PF_NO_SETAFFINITY
+# define PF_NO_SETAFFINITY 0x04000000
+#endif
+
 struct taskset {
 	pid_t		pid;		/* task PID */
 	cpu_set_t	*set;		/* task CPU mask */
@@ -112,6 +116,7 @@ static void __attribute__((__noreturn__)) err_affinity(pid_t pid, int set)
 	err(EXIT_FAILURE, msg, pid ? pid : getpid());
 }
 
+
 static void do_taskset(struct taskset *ts, size_t setsize, cpu_set_t *set)
 {
 	/* read the current mask */
@@ -125,8 +130,22 @@ static void do_taskset(struct taskset *ts, size_t setsize, cpu_set_t *set)
 		return;
 
 	/* set new mask */
-	if (sched_setaffinity(ts->pid, setsize, set) < 0)
+	if (sched_setaffinity(ts->pid, setsize, set) < 0) {
+		uintmax_t flags = 0;
+		struct path_cxt *pc;
+		int errsv = errno;
+
+		if (errno != EPERM
+		    && (pc = ul_new_procfs_path(ts->pid, NULL))
+		    && procfs_process_get_stat_nth(pc, 9, &flags) == 0
+		    && (flags & PF_NO_SETAFFINITY)) {
+			warnx(_("affinity cannot be set due to PF_NO_SETAFFINITY flag set"));
+			errno = EINVAL;
+		} else
+			errno = errsv;
+
 		err_affinity(ts->pid, 1);
+	}
 
 	/* re-read the current mask */
 	if (ts->pid) {