AP_HAL_Linux: fixed signal handler in RCInput_Navio

DMA is getting stopped in the separate method now. This is the best we
can get at the current time. It does yield slightly better experience
and works in the majority of cases.

The patch is a no bulletproof solution, though.

There's a possibility of corruption in case of e.g. a SIGKILL. There's
no signal framework at the time and the commit doesn't add one. That's
why all signals are handled in the same erroneous way. This is not a
good nor a final solution to the issue.

For the issue at hand a better fix might be porting the code to kernel
space but it's a rather tediuos task that we cannot undertake in the
couple of weeks.

libraries/AP_HAL_Linux/RCInput_Navio.cpp

@@ -264,11 +264,16 @@ void LinuxRCInput_Navio::init_dma_cb(dma_cb_t** cbp, uint32_t mode, uint32_t sou
     (*cbp)->stride = stride;
 }
 
-//Non-stoping DMA when the process is finished will lead to crash
-void LinuxRCInput_Navio::stop_dma_and_exit(int param)
+void LinuxRCInput_Navio::stop_dma()
 {
-    dma_reg[RCIN_NAVIO_DMA_CS | RCIN_NAVIO_DMA_CHANNEL << 8] = 0;    // stop dma 
-    exit(1);
+    dma_reg[RCIN_NAVIO_DMA_CS | RCIN_NAVIO_DMA_CHANNEL << 8] = 0;
+}
+
+/* We need to be sure that the DMA is stopped upon termination */
+void LinuxRCInput_Navio::termination_handler(int signum)
+{
+    stop_dma();
+    hal.scheduler->panic("Interrupted");
 }
 
 
@@ -380,7 +385,7 @@ void LinuxRCInput_Navio::set_sigaction()
         //catch all signals (like ctrl+c, ctrl+z, ...) to ensure DMA is disabled
         struct sigaction sa;
         memset(&sa, 0, sizeof(sa));
-        sa.sa_handler = LinuxRCInput_Navio::stop_dma_and_exit;
+        sa.sa_handler = LinuxRCInput_Navio::termination_handler;
         sigaction(i, &sa, NULL);
     }
 }
@@ -413,7 +418,7 @@ LinuxRCInput_Navio::~LinuxRCInput_Navio()
 
 void LinuxRCInput_Navio::deinit()
 {
-    stop_dma_and_exit(0);
+    stop_dma();
 }
 
 //Initializing necessary registers

libraries/AP_HAL_Linux/RCInput_Navio.h

@@ -123,7 +123,8 @@ private:
     void init_PCM();
     void init_DMA();
     void init_buffer();
-    static void stop_dma_and_exit(int param);
+    static void stop_dma();
+    static void termination_handler(int signum);
     void set_sigaction();
     void set_physical_addresses(int version);
     void deinit() override;