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Re: [patch 1/3] Relay Reset Consumed
- From: Andrew Morton <akpm at linux-foundation dot org>
- To: "David J. Wilder" <dwilder at us dot ibm dot com>
- Cc: linux-kernel at vger dot kernel dot org, systemtap at sourceware dot org, Andy Whitcroft <apw at shadowen dot org>
- Date: Wed, 5 Mar 2008 14:12:29 -0800
- Subject: Re: [patch 1/3] Relay Reset Consumed
- References: <1204588311.32186.7.camel@lc4eb748232119.ibm.com>
On Mon, 03 Mar 2008 15:51:50 -0800
"David J. Wilder" <dwilder@us.ibm.com> wrote:
> This patch allows relay channels to be reset i.e. unconsumed.
> Basically allows a 'rewind' function for flight-recorder tracing.
>
> +void relay_reset_consumed(struct rchan *chan)
> +{
> + unsigned int i;
> + struct rchan_buf *prev = NULL;
> +
> + if (!chan)
> + return;
> +
> + for (i = 0; i < NR_CPUS; i++) {
Use of NR_CPUS is usually wrong. In this case it seems you should be using
for_each_possible_cpu().
Also the existing usage of NR_CPUS in relay_subbufs_consumed() should be
switched to using cpu_possible().
New usage of NR_CPUS might be checkpatch-worthy, actually:
akpm:/usr/src/25> grep -l '^+.*NR_CPUS' patches/*.patch
patches/ext4-mm-mballoc-core.patch
patches/git-kvm.patch
patches/git-perfmon.patch
patches/relay-reset-consumed.patch
patches/x86-andi-git-x86.patch
patches/x86-andi-smp-switch-optimize.patch
that's a sample of 1852 patches.
An appropriate warning would be "Usage of NR_CPUS is often wrong - should
you be using cpu_possible(), num_possible_cpus(), for_each_possible_cpu(),
etc?".