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

Will Deacon
2010-08-27T18:07:35Z

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 This check is obsolete here as we do not call oprofile_arch_exit() on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

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