samples/bpf: tracepoint example

modify offwaketime to work with sched/sched_switch tracepoint
instead of kprobe into finish_task_switch

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 22 insertions, 4 deletions

diff --git a/samples/bpf/offwaketime_kern.c b/samples/bpf/offwaketime_kern.c
index c0aa5a9b9c48..983629a31c79 100644
--- a/samples/bpf/offwaketime_kern.c
+++ b/samples/bpf/offwaketime_kern.c
@@ -73,7 +73,7 @@ int waker(struct pt_regs *ctx)
         return 0;
 }
 
-static inline int update_counts(struct pt_regs *ctx, u32 pid, u64 delta)
+static inline int update_counts(void *ctx, u32 pid, u64 delta)
 {
         struct key_t key = {};
         struct wokeby_t *woke;
@@ -100,15 +100,33 @@ static inline int update_counts(struct pt_regs *ctx, u32 pid, u64 delta)
         return 0;
 }
 
+#if 1
+/* taken from /sys/kernel/debug/tracing/events/sched/sched_switch/format */
+struct sched_switch_args {
+        unsigned long long pad;
+        char prev_comm[16];
+        int prev_pid;
+        int prev_prio;
+        long long prev_state;
+        char next_comm[16];
+        int next_pid;
+        int next_prio;
+};
+SEC("tracepoint/sched/sched_switch")
+int oncpu(struct sched_switch_args *ctx)
+{
+        /* record previous thread sleep time */
+        u32 pid = ctx->prev_pid;
+#else
 SEC("kprobe/finish_task_switch")
 int oncpu(struct pt_regs *ctx)
 {
         struct task_struct *p = (void *) PT_REGS_PARM1(ctx);
+        /* record previous thread sleep time */
+        u32 pid = _(p->pid);
+#endif
         u64 delta, ts, *tsp;
-        u32 pid;
 
-        /* record previous thread sleep time */
-        pid = _(p->pid);
         ts = bpf_ktime_get_ns();
         bpf_map_update_elem(&start, &pid, &ts, BPF_ANY);