AP_HAL_Linux: Thread: allow to set stack size

This allows the code that is creating the thread to set the size of the
stack.

libraries/AP_HAL_Linux/Thread.cpp

@@ -154,6 +154,12 @@ bool Thread::start(const char *name, int policy, int prio)
         }
     }
 
+    if (_stack_size) {
+        if (pthread_attr_setstacksize(&attr, _stack_size) != 0) {
+            return false;
+        }
+    }
+
     r = pthread_create(&_ctx, &attr, &Thread::_run_trampoline, this);
     if (r != 0) {
         AP_HAL::panic("Failed to create thread '%s': %s",
@@ -186,6 +192,17 @@ bool PeriodicThread::set_rate(uint32_t rate_hz)
     return true;
 }
 
+bool Thread::set_stack_size(size_t stack_size)
+{
+    if (_started) {
+        return false;
+    }
+
+    _stack_size = stack_size;
+
+    return true;
+}
+
 bool PeriodicThread::_run()
 {
     uint64_t next_run_usec = AP_HAL::micros64() + _period_usec;

libraries/AP_HAL_Linux/Thread.h

@@ -44,6 +44,8 @@ public:
 
     size_t get_stack_usage();
 
+    bool set_stack_size(size_t stack_size);
+
 protected:
     static void *_run_trampoline(void *arg);
 
@@ -64,6 +66,8 @@ protected:
         uint32_t *start;
         uint32_t *end;
     } _stack_debug;
+
+    size_t _stack_size;
 };
 
 class PeriodicThread : public Thread {