AP_Logger: stop logs safely in the block logger and asynchronously where possible

libraries/AP_Logger/AP_Logger_Backend.cpp

@@ -57,7 +57,7 @@ void AP_Logger_Backend::periodic_1Hz()
     if (_rotate_pending && !logging_enabled()) {
         _rotate_pending = false;
         // handle log rotation once we stop logging
-        stop_logging();
+        stop_logging_async();
     }
     df_stats_log();
 }

libraries/AP_Logger/AP_Logger_Backend.h

@@ -60,6 +60,8 @@ public:
      * packet from a client.
      */
     virtual void stop_logging(void) = 0;
+    // asynchronously stop logging, status can be determined through logging_started()
+    virtual void stop_logging_async(void) { stop_logging(); }
 
     void Fill_Format(const struct LogStructure *structure, struct log_Format &pkt);
     void Fill_Format_Units(const struct LogStructure *s, struct log_Format_Units &pkt);

libraries/AP_Logger/AP_Logger_Block.cpp

@@ -526,20 +526,23 @@ uint16_t AP_Logger_Block::get_num_logs(void)
     return (last - first + 1);
 }
 
-// stop logging and flush any remaining data
+// stop logging immediately
 void AP_Logger_Block::stop_logging(void)
 {
     WITH_SEMAPHORE(sem);
 
     log_write_started = false;
 
-    // complete writing any previous log
-    while (writebuf.available()) {
-        write_log_page();
-    }
+    // nuke writing any previous log
     writebuf.clear();
 }
 
+// stop logging and flush any remaining data
+void AP_Logger_Block::stop_logging_async(void)
+{
+    stop_log_pending = true;
+}
+
 // This function starts a new log file in the AP_Logger
 // no actual data should be written to the storage here
 // that should all be handled by the IO thread
@@ -887,12 +890,26 @@ void AP_Logger_Block::io_timer(void)
         return;
     }
 
+    // we have been asked to stop logging, flush everything
+    if (stop_log_pending) {
+        WITH_SEMAPHORE(sem);
+
+        log_write_started = false;
+
+        // complete writing any previous log
+        while (writebuf.available()) {
+            write_log_page();
+        }
+        writebuf.clear();
+        stop_log_pending = false;
+
     // write at most one page
-    if (writebuf.available() >= df_PageSize - sizeof(struct PageHeader)) {
+    } else if (writebuf.available() >= df_PageSize - sizeof(struct PageHeader)) {
         WITH_SEMAPHORE(sem);
 
         write_log_page();
     }
+
 }
 
 // write out a page of log data

libraries/AP_Logger/AP_Logger_Block.h

@@ -28,6 +28,7 @@ public:
     void start_new_log(void) override;
     uint32_t bufferspace_available() override;
     void stop_logging(void) override;
+    void stop_logging_async(void) override;
     bool logging_failed() const override;
     bool logging_started(void) const override { return log_write_started; }
 
@@ -112,6 +113,8 @@ private:
     volatile bool erase_started;
     // were we logging before the erase started?
     volatile bool new_log_pending;
+    // have we been asked to stop logging safely?
+    volatile bool stop_log_pending;
     // latch to make sure we only write out the full message once
     volatile bool chip_full;
     // io thread health