Messages in this thread | | | Subject | Re: [PATCH V2 3/4] oprofile: Abstract the perf-events backend | From | Will Deacon <> | Date | Fri, 27 Aug 2010 11:41:31 +0100 |
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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
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