Re: [PATCH 1/4] oprofile: Handle initialisation failure more gracefully

Robert Richter
2010-08-27T19:51:02Z

On 27.08.10 14:06:45, Will Deacon wrote:
> Hi Robert,
>
> Thanks for taking the time to look at this.
>
> On Fri, 2010-08-27 at 17:38 +0100, Robert Richter wrote:
> > On 27.08.10 11:15:25, Will Deacon wrote:
>
> > > How about something like this? This removes the exit call
> > > from the init code and sets pointers to NULL after they have been
> > > freed. We still have to do some checking so that we don't try to
> > > release a NULL perf event:
> > >
> > > diff --git a/arch/arm/oprofile/common.c b/arch/arm/oprofile/common.c
> > > index 0691176..12253eb 100644
> > > --- a/arch/arm/oprofile/common.c
> > > +++ b/arch/arm/oprofile/common.c
> > > @@ -275,10 +275,12 @@ out:
> > > return ret;
> > > }
> > >
> > > -static void exit_driverfs(void)
> > > +static void __exit exit_driverfs(void)
> > > {
> > > - platform_device_unregister(oprofile_pdev);
> > > - platform_driver_unregister(&oprofile_driver);
> > > + if (!IS_ERR_OR_NULL(oprofile_pdev)) {
> >
> > This check is obsolete here as we do not call oprofile_arch_exit() on
> > failure.
> >
> Sorry, I was being braindead and thought oprofile_arch_exit might be
> called via oprofile_exit. As it happens, this is only called because of
> module_exit so we know that initialisation will have completed.
>
> In light of this and your comments, I've simplified the code. Once
> people are happy with it, I'll post it as a couple of patches:

Looks good to me know, the code is a lot easier. Please send me a
final version. I'm going to apply it on Monday.

Thanks Will,

-Robert

>
> diff --git a/arch/arm/oprofile/common.c b/arch/arm/oprofile/common.c
> index 0691176..c2c4a2e 100644
> --- a/arch/arm/oprofile/common.c
> +++ b/arch/arm/oprofile/common.c
> @@ -275,7 +275,7 @@ out:
> return ret;
> }
>
> -static void exit_driverfs(void)
> +static void __exit exit_driverfs(void)
> {
> platform_device_unregister(oprofile_pdev);
> platform_driver_unregister(&oprofile_driver);
> @@ -359,14 +359,13 @@ int __init oprofile_arch_init(struct oprofile_operations *ops)
> if (!counter_config) {
> pr_info("oprofile: failed to allocate %d "
> "counters\n", perf_num_counters);
> - return -ENOMEM;
> + ret = -ENOMEM;
> + goto out;
> }
>
> ret = init_driverfs();
> - if (ret) {
> - kfree(counter_config);
> - return ret;
> - }
> + if (ret)
> + goto out;
>
> for_each_possible_cpu(cpu) {
> perf_events[cpu] = kcalloc(perf_num_counters,
> @@ -374,9 +373,8 @@ int __init oprofile_arch_init(struct oprofile_operations *ops)
> if (!perf_events[cpu]) {
> pr_info("oprofile: failed to allocate %d perf events "
> "for cpu %d\n", perf_num_counters, cpu);
> - while (--cpu >= 0)
> - kfree(perf_events[cpu]);
> - return -ENOMEM;
> + ret = -ENOMEM;
> + goto out;
> }
> }
>
> @@ -393,28 +391,33 @@ int __init oprofile_arch_init(struct oprofile_operations *ops)
> else
> pr_info("oprofile: using %s\n", ops->cpu_type);
>
> +out:
> + if (ret) {
> + kfree(counter_config);
> + for_each_possible_cpu(cpu)
> + kfree(perf_events[cpu]);
> + }
> +
> return ret;
> }
>
> -void oprofile_arch_exit(void)
> +void __exit oprofile_arch_exit(void)
> {
> int cpu, id;
> struct perf_event *event;
>
> - if (*perf_events) {
> - exit_driverfs();
> - for_each_possible_cpu(cpu) {
> - for (id = 0; id < perf_num_counters; ++id) {
> - event = perf_events[cpu][id];
> - if (event != NULL)
> - perf_event_release_kernel(event);
> - }
> - kfree(perf_events[cpu]);
> + for_each_possible_cpu(cpu) {
> + for (id = 0; id < perf_num_counters; ++id) {
> + event = perf_events[cpu][id];
> + if (event)
> + perf_event_release_kernel(event);
> }
> +
> + kfree(perf_events[cpu]);
> }
>
> - if (counter_config)
> - kfree(counter_config);
> + kfree(counter_config);
> + exit_driverfs();
> }
> #else
> int __init oprofile_arch_init(struct oprofile_operations *ops)
> @@ -422,5 +425,5 @@ int __init oprofile_arch_init(struct oprofile_operations *ops)
> pr_info("oprofile: hardware counters not available\n");
> return -ENODEV;
> }
> -void oprofile_arch_exit(void) {}
> +void __exit oprofile_arch_exit(void) {}
> #endif /* CONFIG_HW_PERF_EVENTS */
> diff --git a/drivers/oprofile/oprof.c b/drivers/oprofile/oprof.c
> index b336cd9..b4a6857 100644
> --- a/drivers/oprofile/oprof.c
> +++ b/drivers/oprofile/oprof.c
> @@ -257,16 +257,9 @@ static int __init oprofile_init(void)
> printk(KERN_INFO "oprofile: using timer interrupt.\n");
> err = oprofile_timer_init(&oprofile_ops);
> if (err)
> - goto out_arch;
> + return err;
> }
> - err = oprofilefs_register();
> - if (err)
> - goto out_arch;
> - return 0;
> -
> -out_arch:
> - oprofile_arch_exit();
> - return err;
> + return oprofilefs_register();
> }
>
>
> Once again, thanks for looking at this and have a good weekend,
>
> Will
>
>
>

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