Support unloading of probe providers

[lttng-ust.git] / liblttng-ust / tracepoint.c

diff --git a/liblttng-ust/tracepoint.c b/liblttng-ust/tracepoint.c
index 14b8231f879fca9d3aa8e3bde5a6a661cbb6b4c2..2c25d46250b603c6ed3e5c987f24aae905ef482a 100644 (file)
--- a/liblttng-ust/tracepoint.c
+++ b/liblttng-ust/tracepoint.c
@@ -107,8 +107,8 @@ struct tracepoint_entry {
        struct lttng_ust_tracepoint_probe *probes;
        int refcount;   /* Number of times armed. 0 if disarmed. */
        int callsite_refcount;  /* how many libs use this tracepoint */
-       const char *signature;
-       char name[0];
+       char *signature;
+       char *name;
 };
 
 struct tp_probes {
@@ -132,6 +132,7 @@ struct callsite_entry {
        struct cds_hlist_node hlist;    /* hash table node */
        struct cds_list_head node;      /* lib list of callsites node */
        struct lttng_ust_tracepoint *tp;
+       bool tp_entry_callsite_ref; /* Has a tp_entry took a ref on this callsite */
 };
 
 /* coverity[+alloc] */
@@ -284,6 +285,8 @@ static struct tracepoint_entry *add_tracepoint(const char *name,
        struct cds_hlist_node *node;
        struct tracepoint_entry *e;
        size_t name_len = strlen(name);
+       size_t sig_len = strlen(signature);
+       size_t sig_off, name_off;
        uint32_t hash;
 
        if (name_len > LTTNG_UST_SYM_NAME_LEN - 1) {
@@ -298,19 +301,29 @@ static struct tracepoint_entry *add_tracepoint(const char *name,
                        return ERR_PTR(-EEXIST);        /* Already there */
                }
        }
+
        /*
-        * Using zmalloc here to allocate a variable length element. Could
-        * cause some memory fragmentation if overused.
+        * Using zmalloc here to allocate a variable length elements: name and
+        * signature. Could cause some memory fragmentation if overused.
         */
-       e = zmalloc(sizeof(struct tracepoint_entry) + name_len + 1);
+       name_off = sizeof(struct tracepoint_entry);
+       sig_off = name_off + name_len + 1;
+
+       e = zmalloc(sizeof(struct tracepoint_entry) + name_len + 1 + sig_len + 1);
        if (!e)
                return ERR_PTR(-ENOMEM);
-       memcpy(&e->name[0], name, name_len + 1);
+       e->name = (char *) e + name_off;
+       memcpy(e->name, name, name_len + 1);
        e->name[name_len] = '\0';
+
+       e->signature = (char *) e + sig_off;
+       memcpy(e->signature, signature, sig_len + 1);
+       e->signature[sig_len] = '\0';
+
        e->probes = NULL;
        e->refcount = 0;
        e->callsite_refcount = 0;
-       e->signature = signature;
+
        cds_hlist_add_head(&e->hlist, head);
        return e;
 }
@@ -405,6 +418,7 @@ static void add_callsite(struct tracepoint_lib * lib, struct lttng_ust_tracepoin
        if (!tp_entry)
                return;
        tp_entry->callsite_refcount++;
+       e->tp_entry_callsite_ref = true;
 }
 
 /*
@@ -417,7 +431,8 @@ static void remove_callsite(struct callsite_entry *e)
 
        tp_entry = get_tracepoint(e->tp->name);
        if (tp_entry) {
-               tp_entry->callsite_refcount--;
+               if (e->tp_entry_callsite_ref)
+                       tp_entry->callsite_refcount--;
                if (tp_entry->callsite_refcount == 0)
                        disable_tracepoint(e->tp);
        }
@@ -453,10 +468,15 @@ static void tracepoint_sync_callsites(const char *name)
                if (strncmp(name, tp->name, LTTNG_UST_SYM_NAME_LEN - 1))
                        continue;
                if (tp_entry) {
+                       if (!e->tp_entry_callsite_ref) {
+                               tp_entry->callsite_refcount++;
+                               e->tp_entry_callsite_ref = true;
+                       }
                        set_tracepoint(&tp_entry, tp,
                                        !!tp_entry->refcount);
                } else {
                        disable_tracepoint(tp);
+                       e->tp_entry_callsite_ref = false;
                }
        }
 }
@@ -545,7 +565,12 @@ tracepoint_add_probe(const char *name, void (*probe)(void), void *data,
        struct lttng_ust_tracepoint_probe *old;
 
        entry = get_tracepoint(name);
-       if (!entry) {
+       if (entry) {
+               if (strcmp(entry->signature, signature) != 0) {
+                       ERR("Tracepoint and probe signature do not match.");
+                       return ERR_PTR(-EINVAL);
+               }
+       } else {
                entry = add_tracepoint(name, signature);
                if (IS_ERR(entry))
                        return (struct lttng_ust_tracepoint_probe *)entry;