Re: Small bug with offline cpus

[christos%astron.com@localhost (Christos Zoulas)]

In article <55E027CD.4010705%m00nbsd.net@localhost>,
Maxime Villard  <max%m00nbsd.net@localhost> wrote:
>Hi,
>a bug I must have spotted some weeks ago: the kernel decrements the
>number of offline cpus even when trying to shutting down one fails.
>How to reproduce:
>
>	# schedctl -p SOME_RANDOM_PROC_PID -A 0
>	# sysctl hw.ncpuonline
>	# cpuctl offline 0     (it fails)
>	# sysctl hw.ncpuonline (one cpu missing)
>
>If you cpuctl too much, the value goes negative. This is not a harmful
>bug.
>
>Index: kern_cpu.c
>===================================================================
>RCS file: /cvsroot/src/sys/kern/kern_cpu.c,v
>retrieving revision 1.70
>diff -u -r1.70 kern_cpu.c
>--- kern_cpu.c	20 Aug 2015 09:45:45 -0000	1.70
>+++ kern_cpu.c	28 Aug 2015 08:51:36 -0000
>@@ -444,7 +444,6 @@
> 		if ((spc->spc_flags & SPCF_OFFLINE) == 0)
> 			return 0;
> 		func = (xcfunc_t)cpu_xc_online;
>-		ncpuonline++;
> 	} else {
> 		if ((spc->spc_flags & SPCF_OFFLINE) != 0)
> 			return 0;
>@@ -463,16 +462,19 @@
> 		if (nonline == 1)
> 			return EBUSY;
> 		func = (xcfunc_t)cpu_xc_offline;
>-		ncpuonline--;
> 	}
> 
> 	where = xc_unicast(0, func, ci, NULL, ci);
> 	xc_wait(where);
> 	if (online) {
> 		KASSERT((spc->spc_flags & SPCF_OFFLINE) == 0);
>-	} else if ((spc->spc_flags & SPCF_OFFLINE) == 0) {
>-		/* If was not set offline, then it is busy */
>-		return EBUSY;
>+		ncpuonline++;
>+	} else {
>+		if ((spc->spc_flags & SPCF_OFFLINE) == 0) {
>+			/* If was not set offline, then it is busy */
>+			return EBUSY;
>+		}
>+		ncpuonline--;
> 	}
> 
> 	spc->spc_lastmod = time_second;
>
>
>Ok?

Ok with me.

christos