svn commit: r309658 - head/sys/vm
Bruce Evans
brde at optusnet.com.au
Wed Dec 7 00:45:01 UTC 2016
On Tue, 6 Dec 2016, Mark Johnston wrote:
> Log:
> Provide dummy sysctls for v_cache_count and v_tcached.
>
> Some utilities (notably top(1)) exit if any of their input sysctls don't
> exist, and the removal of the above-mentioned PG_CACHE-related sysctls
> makes it difficult to run such utilities on different versions of the
> kernel without recompiling.
>
> Requested by: bde
Thanks.
> Modified: head/sys/vm/vm_meter.c
> ==============================================================================
> --- head/sys/vm/vm_meter.c Tue Dec 6 22:48:28 2016 (r309657)
> +++ head/sys/vm/vm_meter.c Tue Dec 6 22:52:45 2016 (r309658)
> @@ -314,3 +314,14 @@ VM_STATS_VM(v_forkpages, "VM pages affec
> VM_STATS_VM(v_vforkpages, "VM pages affected by vfork()");
> VM_STATS_VM(v_rforkpages, "VM pages affected by rfork()");
> VM_STATS_VM(v_kthreadpages, "VM pages affected by fork() by kernel");
> +
> +#ifndef BURN_BRIDGES
> +/*
> + * Provide compatibility sysctls for the benefit of old utilities which exit
> + * with an error if they cannot be found.
> + */
> +SYSCTL_UINT(_vm_stats_vm, OID_AUTO, v_cache_count, CTLFLAG_RD,
> + (u_int *)NULL, 0, "Dummy for compatibility");
> +SYSCTL_UINT(_vm_stats_vm, OID_AUTO, v_tcached, CTLFLAG_RD,
> + (u_int *)NULL, 0, "Dummy for compatibility");
> +#endif
I don't like casting NULL, but SYSCTL_* enforces type safety for pointers
to variables in a way that breaks normal use of NULL.
You are supposed to obfuscate this by spelling the value as SYSCTL_UINT_NULL.
This is actually documented in sysctl(9).
Bruc
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