Commit-ID: 0e7e46b6491b016693b20de253d579abcd0bee40
Gitweb: https://git.kernel.org/tip/0e7e46b6491b016693b20de253d579abcd0bee40
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Tue, 9 Jan 2018 21:23:02 +0100
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 24 Jan 2018 10:07:25 +0100
perf/core: Fix ctx::mutex deadlock
Lockdep whinged like:
sys_perf_event_open()
perf_event_alloc()
perf_try_init_event()
perf_swevent_init()
swevent_hlist_get()
perf_event_init_cpu()
sys_perf_event_open()
mutex_lock_double()
And while we need that perf_event_ctx_lock_nested() for HW PMUs such
that they can iterate the sibling list, trying to match it to the
available counters, the software PMUs need do no such thing. Exclude
them.
In particular the swevent triggers the above invertion, while the
tpevent pmu triggers a more elaborate one through their event_mutex.
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/events/core.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 816f83d..5d8f403 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -9199,7 +9199,13 @@ static int perf_try_init_event(struct pmu *pmu, struct perf_event *event)
if (!try_module_get(pmu->module))
return -ENODEV;
- if (event->group_leader != event) {
+ /*
+ * A number of pmu->event_init() methods iterate the sibling_list to,
+ * for example, validate if the group fits on the PMU. Therefore,
+ * if this is a sibling event, acquire the ctx->mutex to protect
+ * the sibling_list.
+ */
+ if (event->group_leader != event && pmu->task_ctx_nr != perf_sw_context) {
/*
* This ctx->mutex can nest when we're called through
* inheritance. See the perf_event_ctx_lock_nested() comment.
--
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