linux-kernel - [PATCH v1 1/2] perf lock contention: Support pre-5.14 kernels

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Message-Id: <20230408055208.1283832-1-irogers@google.com>
Date:   Fri,  7 Apr 2023 22:52:07 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        bpf@...r.kernel.org
Subject: [PATCH v1 1/2] perf lock contention: Support pre-5.14 kernels

struct rq's variable __lock was renamed from lock in 5.14.

Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/perf/util/bpf_skel/lock_contention.bpf.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/bpf_skel/lock_contention.bpf.c b/tools/perf/util/bpf_skel/lock_contention.bpf.c
index 23f6e63544ed..8911e2a077d8 100644
--- a/tools/perf/util/bpf_skel/lock_contention.bpf.c
+++ b/tools/perf/util/bpf_skel/lock_contention.bpf.c
@@ -418,6 +418,14 @@ int contention_end(u64 *ctx)
 
 extern struct rq runqueues __ksym;
 
+struct rq__old {
+	raw_spinlock_t lock;
+} __attribute__((preserve_access_index));
+
+struct rq__new {
+	raw_spinlock_t __lock;
+} __attribute__((preserve_access_index));
+
 SEC("raw_tp/bpf_test_finish")
 int BPF_PROG(collect_lock_syms)
 {
@@ -426,11 +434,16 @@ int BPF_PROG(collect_lock_syms)
 
 	for (int i = 0; i < MAX_CPUS; i++) {
 		struct rq *rq = bpf_per_cpu_ptr(&runqueues, i);
+		struct rq__new *rq_new = (void *)rq;
+		struct rq__old *rq_old = (void *)rq;
 
 		if (rq == NULL)
 			break;
 
-		lock_addr = (__u64)&rq->__lock;
+		if (bpf_core_field_exists(rq_new->__lock))
+			lock_addr = (__u64)&rq_new->__lock;
+		else
+			lock_addr = (__u64)&rq_old->lock;
 		lock_flag = LOCK_CLASS_RQLOCK;
 		bpf_map_update_elem(&lock_syms, &lock_addr, &lock_flag, BPF_ANY);
 	}
-- 
2.40.0.577.gac1e443424-goog