lkml.org 
[lkml]   [2023]   [Nov]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    Date
    SubjectRe: [PATCH 01/13] perf: Simplify perf_event_alloc() error path
    Hi Jiri and Peter,

    On Fri, Nov 3, 2023 at 5:38 AM Jiri Olsa <olsajiri@gmail.com> wrote:
    >
    > On Thu, Nov 02, 2023 at 04:09:20PM +0100, Peter Zijlstra wrote:
    >
    > SNIP
    >
    > > @@ -11936,24 +11957,24 @@ perf_event_alloc(struct perf_event_attr
    > > */
    > > if (pmu->task_ctx_nr == perf_invalid_context && (task || cgroup_fd != -1)) {
    > > err = -EINVAL;
    > > - goto err_pmu;
    > > + goto err;
    > > }
    > >
    > > if (event->attr.aux_output &&
    > > !(pmu->capabilities & PERF_PMU_CAP_AUX_OUTPUT)) {
    > > err = -EOPNOTSUPP;
    > > - goto err_pmu;
    > > + goto err;
    > > }
    > >
    > > if (cgroup_fd != -1) {
    > > err = perf_cgroup_connect(cgroup_fd, event, attr, group_leader);
    > > if (err)
    > > - goto err_pmu;
    > > + goto err;
    > > }
    > >
    > > err = exclusive_event_init(event);
    > > if (err)
    > > - goto err_pmu;
    > > + goto err;
    > >
    > > if (has_addr_filter(event)) {
    > > event->addr_filter_ranges = kcalloc(pmu->nr_addr_filters,
    > > @@ -11961,7 +11982,7 @@ perf_event_alloc(struct perf_event_attr
    > > GFP_KERNEL);
    > > if (!event->addr_filter_ranges) {
    > > err = -ENOMEM;
    > > - goto err_per_task;
    > > + goto err;
    > > }
    > >
    > > /*
    > > @@ -11986,41 +12007,21 @@ perf_event_alloc(struct perf_event_attr
    > > if (event->attr.sample_type & PERF_SAMPLE_CALLCHAIN) {
    > > err = get_callchain_buffers(attr->sample_max_stack);
    > > if (err)
    > > - goto err_addr_filters;
    > > + goto err;
    > > }
    > > }
    > >
    > > err = security_perf_event_alloc(event);
    > > if (err)
    > > - goto err_callchain_buffer;
    > > + goto err;
    > >
    > > /* symmetric to unaccount_event() in _free_event() */
    > > account_event(event);
    > >
    > > return event;
    > >
    > > -err_callchain_buffer:
    > > - if (!event->parent) {
    > > - if (event->attr.sample_type & PERF_SAMPLE_CALLCHAIN)
    > > - put_callchain_buffers();
    > > - }
    >
    > hum, so this is now called all the time via __free_event, but it should
    > be called only if we passed get_callchain_buffers call.. this could screw
    > up nr_callchain_events number eventually no?

    Looks like so.

    >
    > jirka
    >
    > > -err_addr_filters:
    > > - kfree(event->addr_filter_ranges);
    > > -
    > > -err_per_task:
    > > - exclusive_event_destroy(event);
    > > -
    > > -err_pmu:
    > > - if (is_cgroup_event(event))
    > > - perf_detach_cgroup(event);
    > > - if (event->destroy)
    > > - event->destroy(event);
    > > - module_put(pmu->module);

    I'm afraid of this part. If it failed at perf_init_event(), it might
    call event->destroy() already. I saw you cleared event->pmu
    in the failure path. Maybe we need the same thing for the
    event->destroy.

    Thanks,
    Namhyung


    > > -err_ns:
    > > - if (event->hw.target)
    > > - put_task_struct(event->hw.target);
    > > - call_rcu(&event->rcu_head, free_event_rcu);
    > > -
    > > +err:
    > > + __free_event(event);
    > > return ERR_PTR(err);
    > > }
    > >
    > >
    > >

    \
     
     \ /
      Last update: 2023-11-20 13:48    [W:3.734 / U:0.004 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site