Fix hardirq/softirq value init logic (#253)

I did not realize that valp was pointing to the *actual* kernel ebpf value, and that the update we do here will persist for the value sitting in the map.
netdata · Aug 30, 2021 · abc1da7 · abc1da7
1 parent bc6e88e
commit abc1da7
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Showing 2 changed files with 15 additions and 18 deletions.
diff --git a/kernel/hardirq_kern.c b/kernel/hardirq_kern.c
@@ -41,16 +41,15 @@ int netdata_irq_handler_entry(struct netdata_irq_handler_entry *ptr)
 
     key.irq = ptr->irq;
     valp = bpf_map_lookup_elem(&tbl_hardirq, &key);
-    if (!valp) {
+    if (valp) {
+        valp->ts = bpf_ktime_get_ns();
+    } else {
         val.latency = 0;
+        val.ts = bpf_ktime_get_ns();
         TP_DATA_LOC_READ_CONST(val.name, ptr, ptr->data_loc_name, NETDATA_HARDIRQ_NAME_LEN);
-    } else {
-        val.latency = valp->latency;
+        bpf_map_update_elem(&tbl_hardirq, &key, &val, BPF_ANY);
     }
 
-    val.ts = bpf_ktime_get_ns();
-    bpf_map_update_elem(&tbl_hardirq, &key, &val, BPF_ANY);
-
     return 0;
 }
 
@@ -85,15 +84,14 @@ int netdata_irq_ ##__type(struct netdata_irq_vectors_entry *ptr)              \
                                                                               \
     idx = __enum_idx;                                                         \
     valp = bpf_map_lookup_elem(&tbl_hardirq_static, &idx);                    \
-    if (!valp) {                                                              \
-        val.latency = 0;                                                      \
+    if (valp) {                                                               \
+        valp->ts = bpf_ktime_get_ns();                                        \
     } else {                                                                  \
-        val.latency = valp->latency;                                          \
+        val.latency = 0;                                                      \
+        val.ts = bpf_ktime_get_ns();                                          \
+        bpf_map_update_elem(&tbl_hardirq_static, &idx, &val, BPF_ANY);        \
     }                                                                         \
                                                                               \
-    val.ts = bpf_ktime_get_ns();                                              \
-    bpf_map_update_elem(&tbl_hardirq_static, &idx, &val, BPF_ANY);            \
-                                                                              \
     return 0;                                                                 \
 }
 

diff --git a/kernel/softirq_kern.c b/kernel/softirq_kern.c
@@ -34,15 +34,14 @@ int netdata_softirq_entry(struct netdata_softirq_entry *ptr)
     }
 
     valp = bpf_map_lookup_elem(&tbl_softirq, &vec);
-    if (!valp) {
-        val.latency = 0;
+    if (valp) {
+        valp->ts = bpf_ktime_get_ns();
     } else {
-        val.latency = valp->latency;
+        val.latency = 0;
+        val.ts = bpf_ktime_get_ns();
+        bpf_map_update_elem(&tbl_softirq, &vec, &val, BPF_ANY);
     }
 
-    val.ts = bpf_ktime_get_ns();
-    bpf_map_update_elem(&tbl_softirq, &vec, &val, BPF_ANY);
-
     return 0;
 }