diff options
author | Peter Zijlstra <peterz@infradead.org> | 2013-10-03 16:02:23 +0200 |
---|---|---|
committer | Ingo Molnar <mingo@kernel.org> | 2013-10-04 09:58:53 +0200 |
commit | 9886167d20c0720dcfb01e62cdff4d906b226f43 (patch) | |
tree | dff8fb937ae2c73fe474263da0e906aa77d6ae54 /include/linux | |
parent | cac6653529eeac9b661fc8342c47d849c3adb085 (diff) |
perf: Fix perf_pmu_migrate_context
While auditing the list_entry usage due to a trinity bug I found that
perf_pmu_migrate_context violates the rules for
perf_event::event_entry.
The problem is that perf_event::event_entry is a RCU list element, and
hence we must wait for a full RCU grace period before re-using the
element after deletion.
Therefore the usage in perf_pmu_migrate_context() which re-uses the
entry immediately is broken. For now introduce another list_head into
perf_event for this specific usage.
This doesn't actually fix the trinity report because that never goes
through this code.
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-mkj72lxagw1z8fvjm648iznw@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'include/linux')
-rw-r--r-- | include/linux/perf_event.h | 24 |
1 files changed, 23 insertions, 1 deletions
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 866e85c5eb9..c8ba627c1d6 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -294,9 +294,31 @@ struct ring_buffer; */ struct perf_event { #ifdef CONFIG_PERF_EVENTS - struct list_head group_entry; + /* + * entry onto perf_event_context::event_list; + * modifications require ctx->lock + * RCU safe iterations. + */ struct list_head event_entry; + + /* + * XXX: group_entry and sibling_list should be mutually exclusive; + * either you're a sibling on a group, or you're the group leader. + * Rework the code to always use the same list element. + * + * Locked for modification by both ctx->mutex and ctx->lock; holding + * either sufficies for read. + */ + struct list_head group_entry; struct list_head sibling_list; + + /* + * We need storage to track the entries in perf_pmu_migrate_context; we + * cannot use the event_entry because of RCU and we want to keep the + * group in tact which avoids us using the other two entries. + */ + struct list_head migrate_entry; + struct hlist_node hlist_entry; int nr_siblings; int group_flags; |