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

From: [email-masked] (Robert Richter)
Date: Fri, 27 Aug 2010 21:47:50 +0200

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 This check is obsolete here as we do not call oprofile_arch_exit() on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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