Merge "Use sequence number to check if to reload atrace tags." am: 445234c76c am: d371ad8665
Change-Id: Ic57e29442cfc905444a4f14983a39aa67e01a80c
diff --git a/libcutils/include/cutils/trace.h b/libcutils/include/cutils/trace.h
index 79b4b35..e12c32c 100644
--- a/libcutils/include/cutils/trace.h
+++ b/libcutils/include/cutils/trace.h
@@ -25,7 +25,6 @@
#include <sys/cdefs.h>
#include <sys/types.h>
#include <unistd.h>
-
#include <cutils/compiler.h>
__BEGIN_DECLS
@@ -89,6 +88,12 @@
#error ATRACE_TAG must be defined to be one of the tags defined in cutils/trace.h
#endif
+// Set this to 0 to revert to the old Binder-based atrace implementation.
+// This is only here in case rollbacks do not apply cleanly.
+// TODO(fmayer): Remove this once we are confident this won't need to be
+// rolled back, no later than 2020-03-01.
+#define ATRACE_SHMEM 1
+
/**
* Opens the trace file for writing and reads the property for initial tags.
* The atrace.tags.enableflags property sets the tags to trace.
@@ -116,11 +121,15 @@
* prevent tracing within the Zygote process.
*/
void atrace_set_tracing_enabled(bool enabled);
-
/**
- * Flag indicating whether setup has been completed, initialized to 0.
- * Nonzero indicates setup has completed.
- * Note: This does NOT indicate whether or not setup was successful.
+ * If !ATRACE_SHMEM:
+ * Flag indicating whether setup has been completed, initialized to 0.
+ * Nonzero indicates setup has completed.
+ * Note: This does NOT indicate whether or not setup was successful.
+ * If ATRACE_SHMEM:
+ * This is always set to false. This forces code that uses an old version
+ * of this header to always call into atrace_setup, in which we call
+ * atrace_init unconditionally.
*/
extern atomic_bool atrace_is_ready;
@@ -143,6 +152,12 @@
* This can be explicitly run to avoid setup delay on first trace function.
*/
#define ATRACE_INIT() atrace_init()
+#define ATRACE_GET_ENABLED_TAGS() atrace_get_enabled_tags()
+
+#if ATRACE_SHMEM
+void atrace_init();
+uint64_t atrace_get_enabled_tags();
+#else
static inline void atrace_init()
{
if (CC_UNLIKELY(!atomic_load_explicit(&atrace_is_ready, memory_order_acquire))) {
@@ -155,12 +170,12 @@
* It can be used as a guard condition around more expensive trace calculations.
* Every trace function calls this, which ensures atrace_init is run.
*/
-#define ATRACE_GET_ENABLED_TAGS() atrace_get_enabled_tags()
static inline uint64_t atrace_get_enabled_tags()
{
atrace_init();
return atrace_enabled_tags;
}
+#endif
/**
* Test if a given tag is currently enabled.
diff --git a/libcutils/trace-container.cpp b/libcutils/trace-container.cpp
index d981f8f..c23d5e2 100644
--- a/libcutils/trace-container.cpp
+++ b/libcutils/trace-container.cpp
@@ -39,6 +39,11 @@
static pthread_mutex_t atrace_enabling_mutex = PTHREAD_MUTEX_INITIALIZER;
static pthread_rwlock_t atrace_container_sock_rwlock = PTHREAD_RWLOCK_INITIALIZER;
+static void atrace_seq_number_changed(uint32_t, uint32_t seq_no) {
+ pthread_once(&atrace_once_control, atrace_init_once);
+ atomic_store_explicit(&last_sequence_number, seq_no, memory_order_relaxed);
+}
+
static bool atrace_init_container_sock()
{
pthread_rwlock_wrlock(&atrace_container_sock_rwlock);
diff --git a/libcutils/trace-dev.cpp b/libcutils/trace-dev.cpp
index bff16c1..2ee39d3 100644
--- a/libcutils/trace-dev.cpp
+++ b/libcutils/trace-dev.cpp
@@ -37,12 +37,39 @@
} else {
atrace_enabled_tags = atrace_get_property();
}
+#if !ATRACE_SHMEM
atomic_store_explicit(&atrace_is_ready, true, memory_order_release);
+#endif
+}
+
+static void atrace_seq_number_changed(uint32_t prev_seq_no, uint32_t seq_no) {
+ if (!atomic_load_explicit(&atrace_is_enabled, memory_order_acquire)) {
+ return;
+ }
+
+ // Someone raced us.
+ if (!atomic_compare_exchange_strong(&last_sequence_number, &prev_seq_no, seq_no)) {
+ return;
+ }
+
+ if (CC_UNLIKELY(prev_seq_no == kSeqNoNotInit)) {
+#if defined(__BIONIC__)
+ const prop_info* new_pi = __system_property_find("debug.atrace.tags.enableflags");
+ if (new_pi) atrace_property_info = new_pi;
+#endif
+ pthread_once(&atrace_once_control, atrace_init_once);
+ }
+
+ atrace_update_tags();
}
void atrace_setup()
{
+#if ATRACE_SHMEM
+ atrace_init();
+#else
pthread_once(&atrace_once_control, atrace_init_once);
+#endif
}
void atrace_begin_body(const char* name)
diff --git a/libcutils/trace-dev.inc b/libcutils/trace-dev.inc
index e3da77b..a57a4c5 100644
--- a/libcutils/trace-dev.inc
+++ b/libcutils/trace-dev.inc
@@ -34,6 +34,11 @@
#include <log/log.h>
#include <log/log_properties.h>
+#if defined(__BIONIC__)
+#define _REALLY_INCLUDE_SYS__SYSTEM_PROPERTIES_H_
+#include <sys/_system_properties.h>
+#endif
+
/**
* Maximum size of a message that can be logged to the trace buffer.
* Note this message includes a tag, the pid, and the string given as the name.
@@ -41,12 +46,57 @@
*/
#define ATRACE_MESSAGE_LENGTH 1024
-atomic_bool atrace_is_ready = ATOMIC_VAR_INIT(false);
-int atrace_marker_fd = -1;
-uint64_t atrace_enabled_tags = ATRACE_TAG_NOT_READY;
-static bool atrace_is_debuggable = false;
-static atomic_bool atrace_is_enabled = ATOMIC_VAR_INIT(true);
-static pthread_mutex_t atrace_tags_mutex = PTHREAD_MUTEX_INITIALIZER;
+constexpr uint32_t kSeqNoNotInit = static_cast<uint32_t>(-1);
+
+atomic_bool atrace_is_ready = ATOMIC_VAR_INIT(false);
+int atrace_marker_fd = -1;
+uint64_t atrace_enabled_tags = ATRACE_TAG_NOT_READY;
+static bool atrace_is_debuggable = false;
+static atomic_bool atrace_is_enabled = ATOMIC_VAR_INIT(true);
+static pthread_mutex_t atrace_tags_mutex = PTHREAD_MUTEX_INITIALIZER;
+
+/**
+ * Sequence number of debug.atrace.tags.enableflags the last time the enabled
+ * tags were reloaded.
+ **/
+static _Atomic(uint32_t) last_sequence_number = ATOMIC_VAR_INIT(kSeqNoNotInit);
+
+#if defined(__BIONIC__)
+// All zero prop_info that has a sequence number of 0. This is easier than
+// depending on implementation details of the property implementation.
+//
+// prop_info is static_assert-ed to be 96 bytes, which cannot change due to
+// ABI compatibility.
+alignas(uint64_t) static char empty_pi[96];
+static const prop_info* atrace_property_info = reinterpret_cast<const prop_info*>(empty_pi);
+#endif
+
+#if ATRACE_SHMEM
+
+/**
+ * This is called when the sequence number of debug.atrace.tags.enableflags
+ * changes and we need to reload the enabled tags.
+ **/
+static void atrace_seq_number_changed(uint32_t prev_seq_no, uint32_t seq_no);
+
+void atrace_init() {
+#if defined(__BIONIC__)
+ uint32_t seq_no = __system_property_serial(atrace_property_info); // Acquire semantics.
+#else
+ uint32_t seq_no = 0;
+#endif
+ uint32_t prev_seq_no = atomic_load_explicit(&last_sequence_number, memory_order_relaxed);
+ if (CC_UNLIKELY(seq_no != prev_seq_no)) {
+ atrace_seq_number_changed(prev_seq_no, seq_no);
+ }
+}
+
+uint64_t atrace_get_enabled_tags()
+{
+ atrace_init();
+ return atrace_enabled_tags;
+}
+#endif
// Set whether this process is debuggable, which determines whether
// application-level tracing is allowed when the ro.debuggable system property
@@ -136,7 +186,7 @@
void atrace_update_tags()
{
uint64_t tags;
- if (CC_UNLIKELY(atomic_load_explicit(&atrace_is_ready, memory_order_acquire))) {
+ if (ATRACE_SHMEM || CC_UNLIKELY(atomic_load_explicit(&atrace_is_ready, memory_order_acquire))) {
if (atomic_load_explicit(&atrace_is_enabled, memory_order_acquire)) {
tags = atrace_get_property();
pthread_mutex_lock(&atrace_tags_mutex);
diff --git a/libcutils/trace-host.cpp b/libcutils/trace-host.cpp
index d47cc18..c21d0ee 100644
--- a/libcutils/trace-host.cpp
+++ b/libcutils/trace-host.cpp
@@ -30,3 +30,10 @@
void atrace_async_end_body(const char* /*name*/, int32_t /*cookie*/) {}
void atrace_int_body(const char* /*name*/, int32_t /*value*/) {}
void atrace_int64_body(const char* /*name*/, int64_t /*value*/) {}
+#if ATRACE_SHMEM
+void atrace_init() {}
+uint64_t atrace_get_enabled_tags()
+{
+ return ATRACE_TAG_NOT_READY;
+}
+#endif