MINOR: trace: implement tracing disabling API

Define a set of functions to temporarily disable/reactivate tracing for
the current thread. This could be useful when wanting to quickly remove
tracing output for some code parts.

The API relies on a disable/resume set of functions, with a thread-local
counter. This counter is tested under __trace_enabled(). It is a
cumulative value so that the same count of resume must be issued after
several disable usage. There is also the possibility to force reset the
counter to 0 before restoring the old value.

This should be backported up to 3.1.

(cherry picked from commit 9d155ca7064290d3280621c85443221fa13334b2)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>

diff --git a/include/haproxy/tinfo-t.h b/include/haproxy/tinfo-t.h
index 3db77e5..991786f 100644 (file)
--- a/include/haproxy/tinfo-t.h
+++ b/include/haproxy/tinfo-t.h
@@ -136,8 +136,9 @@ struct thread_ctx {
        unsigned int nb_tasks;              /* number of tasks allocated on this thread */
        uint8_t tl_class_mask;              /* bit mask of non-empty tasklets classes */
        uint8_t bufq_map;                   /* one bit per non-empty buffer_wq */
+       uint8_t trc_disable_ctr;            /* cumulative counter to temporarily disable tracing */
 
-       // 2 bytes hole here
+       // 1 byte hole here
        unsigned int nb_rhttp_conns;        /* count of current conns used for active reverse HTTP */
        struct sched_activity *sched_profile_entry; /* profile entry in use by the current task/tasklet, only if sched_wake_date>0 */
 

diff --git a/include/haproxy/trace.h b/include/haproxy/trace.h
index ce94289..cab1129 100644 (file)
--- a/include/haproxy/trace.h
+++ b/include/haproxy/trace.h
@@ -206,6 +206,48 @@ static inline char trace_event_char(uint64_t conf, uint64_t ev)
        return (conf & ev) ? '+' : '-';
 }
 
+/* Temporarily disable trace using a cumulative counter. If called multiple
+ * times, the same number of resume must be used to reactivate tracing.
+ *
+ * Returns the incremented counter value or 0 if already at the maximum value.
+ */
+static inline uint8_t trace_disable(void)
+{
+       if (unlikely(th_ctx->trc_disable_ctr == UCHAR_MAX))
+               return 0;
+       return ++th_ctx->trc_disable_ctr;
+}
+
+/* Resume tracing after a temporarily disabling. It may be called several times
+ * as disable operation is cumulative.
+ */
+static inline void trace_resume(void)
+{
+       if (th_ctx->trc_disable_ctr)
+               --th_ctx->trc_disable_ctr;
+}
+
+/* Resume tracing immediately even after multiple disable operations.
+ *
+ * Returns the old counter value. Useful to reactivate trace disabling at the
+ * previous level.
+ */
+static inline uint8_t trace_force_resume(void)
+{
+       const int val = th_ctx->trc_disable_ctr;
+       th_ctx->trc_disable_ctr = 0;
+       return val;
+}
+
+/* Set trace disabling counter to <disable>. Mostly useful with the value
+ * returned from trace_force_resume() to restore tracing disable status to the
+ * previous level.
+ */
+static inline void trace_reset_disable(uint8_t disable)
+{
+       th_ctx->trc_disable_ctr = disable;
+}
+
 #endif /* _HAPROXY_TRACE_H */
 
 /*

diff --git a/src/trace.c b/src/trace.c
index cc49ed9..64af370 100644 (file)
--- a/src/trace.c
+++ b/src/trace.c
@@ -97,9 +97,13 @@ int __trace_enabled(enum trace_level level, uint64_t mask, struct trace_source *
        /* in case we also follow another one (e.g. session) */
        origin = HA_ATOMIC_LOAD(&src->follow);
 
+       /* Trace can be temporarily disabled via trace_disable(). */
        if (likely(src->state == TRACE_STATE_STOPPED) && !origin)
                return 0;
 
+       if (th_ctx->trc_disable_ctr)
+               return 0;
+
        /* check that at least one action is interested by this event */
        if (((src->report_events | src->start_events | src->pause_events | src->stop_events) & mask) == 0)
                return 0;