Hi Matt,

I'm still not happy with the init/exit alloc/free code:

On Thu, 2010-08-26 at 20:09 +0100, Matt Fleming wrote:

[...]

+int oprofile_perf_init(void)
+{
+       u32 counter_size = sizeof(struct op_counter_config);
+       int cpu;
+
+       counter_config = kcalloc(perf_num_counters, counter_size, GFP_KERNEL);
+
+       if (!counter_config) {
+               pr_info("oprofile: failed to allocate %d "
+                               "counters\n", perf_num_counters);
+               return -ENOMEM;
+       }
+
+       for_each_possible_cpu(cpu) {
+               perf_events[cpu] = kcalloc(perf_num_counters,
+                               sizeof(struct perf_event *), GFP_KERNEL);
+               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]);
+                       kfree(counter_config);
+                       return -ENOMEM;
+               }
+       }
+
+       return 0;
+}

So here, if the perf_events allocation fails for a cpu, we free the
stuff we've already allocated [including counter_config] and return
-ENOMEM. Looking at drivers/oprofile/oprof.c:

static int __init oprofile_init(void)
{
	int err;

	err = oprofile_arch_init(&oprofile_ops);
	if (err < 0 || timer) {
		printk(KERN_INFO "oprofile: using timer interrupt.\n");
		err = oprofile_timer_init(&oprofile_ops);
		if (err)
			goto out_arch;
	}
	err = oprofilefs_register();
	if (err)
		goto out_arch;
	return 0;

out_arch:
	oprofile_arch_exit();
	return err;
}

So now, if timer_init fails or oprofilefs_register fails, we will
call oprofile_arch_exit, which calls oprofile_perf_exit:

+void oprofile_perf_exit(void)
+{
+       int id, cpu;
+
+       for_each_possible_cpu(cpu) {
+               for (id = 0; id < perf_num_counters; ++id)
+                       oprofile_destroy_counter(cpu, id);
+
+               kfree(perf_events[cpu]);
+       }
+
+       kfree(counter_config);
+}

meaning that we will free everything again! This is what I
was trying to avoid in patch 1/4, by moving the counter_config
freeing into the *_exit function. Looking at it again, I think
all the freeing should be moved to the *_exit function and the init
function should just return error when allocation fails. What do you
think?

+/*
+ * Create active perf events based on the perviously configured
+ * attributes.
+ */

typo :)

For what it's worth, I tested the series on my Cortex-A9 board and
everything seemed to work fine. I'll give the patches another spin when
we've sorted out these memory issues.

Cheers,

Will