Messages in this thread | | | Date | Thu, 22 Mar 2012 14:06:29 +0530 | From | "Srivatsa S. Bhat" <> | Subject | Re: [PATCH 2/2] x86, mce: Add persistent MCE event |
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On 03/21/2012 08:04 PM, Borislav Petkov wrote:
> From: Borislav Petkov <borislav.petkov@amd.com> > > Add the necessary glue to enable the mce_record tracepoint on boot, > turning it into a persistent event. This exports the MCE buffer through > a debugfs per-CPU file which a userspace daemon can read and then > process the received error data further. > > Signed-off-by: Borislav Petkov <borislav.petkov@amd.com> > --- > arch/x86/kernel/cpu/mcheck/mce.c | 53 ++++++++++++++++++++++++++++++++++++++ > 1 file changed, 53 insertions(+) > > diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c > index 5a11ae2e9e91..791c4633d771 100644 > --- a/arch/x86/kernel/cpu/mcheck/mce.c > +++ b/arch/x86/kernel/cpu/mcheck/mce.c > @@ -95,6 +95,13 @@ static DECLARE_WAIT_QUEUE_HEAD(mce_chrdev_wait); > static DEFINE_PER_CPU(struct mce, mces_seen); > static int cpu_missing; > > +static struct perf_event_attr pattr = { > + .type = PERF_TYPE_TRACEPOINT, > + .size = sizeof(pattr), > + .sample_type = PERF_SAMPLE_RAW, > + .persistent = 1, > +}; > + > /* MCA banks polled by the period polling timer for corrected events */ > DEFINE_PER_CPU(mce_banks_t, mce_poll_banks) = { > [0 ... BITS_TO_LONGS(MAX_NR_BANKS)-1] = ~0UL > @@ -102,6 +109,8 @@ DEFINE_PER_CPU(mce_banks_t, mce_poll_banks) = { > > static DEFINE_PER_CPU(struct work_struct, mce_work); > > +static DEFINE_PER_CPU(struct pers_event_desc, mce_ev); > + > /* > * CPU/chipset specific EDAC code can register a notifier call here to print > * MCE errors in a human-readable form. > @@ -2109,6 +2118,50 @@ static void __cpuinit mce_reenable_cpu(void *h) > } > } > > +static __init int mcheck_init_persistent_event(void) > +{ > + > +#define MCE_RECORD_FNAME_SZ 14 > +#define MCE_BUF_PAGES 4 > + > + int cpu, err = 0; > + char buf[MCE_RECORD_FNAME_SZ]; > + > + pattr.config = event_mce_record.event.type; > + pattr.sample_period = 1; > + pattr.wakeup_events = 1; > + > + get_online_cpus(); > + > + for_each_online_cpu(cpu) { > + struct pers_event_desc *d = &per_cpu(mce_ev, cpu); > + > + snprintf(buf, MCE_RECORD_FNAME_SZ, "mce_record%d", cpu); > + d->dfs_name = buf; > + d->pattr = &pattr; > + > + if (perf_add_persistent_on_cpu(cpu, d, mce_get_debugfs_dir(), > + MCE_BUF_PAGES)) > + goto err_unwind; > + } > + goto unlock; > + > +err_unwind: > + err = -EINVAL; > + for (--cpu; cpu >= 0; cpu--) > + perf_rm_persistent_on_cpu(cpu, &per_cpu(mce_ev, cpu)); > +
*Totally* theoretical question: How do you know that the cpu_online_mask isn't sparse? In other words, what if some CPUs weren't booted? Then this for-loop wouldn't be very good..
Oh, now I see that perf_rm_persistent_on_cpu() probably handles that case well.. So no issues I guess.. ?
(Moreover, we will probably have bigger issues at hand if some CPU didn't boot..)
(The code looked funny, so I thought of pointing it out, whether or not it actually is worrisome. Sorry for the noise, if any).
> +unlock: > + put_online_cpus(); > + > + return err; > +} > + > +/* > + * This has to run after event_trace_init() > + */ > +device_initcall(mcheck_init_persistent_event); > + > /* Get notified when a cpu comes on/off. Be hotplug friendly. */ > static int __cpuinit > mce_cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
Regards, Srivatsa S. Bhat
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