Fixed atomic access to flags in sys.execute.

This seems to fix the bug that caused Grbl to hang during some operations,
especially jogging.

limits.c

@@ -86,7 +86,7 @@ ISR(LIMIT_INT_vect) // DEFAULT: Limit pin change interrupt process.
   if (sys.state != STATE_ALARM) { 
     if (bit_isfalse(sys.execute,EXEC_ALARM)) {
       mc_reset(); // Initiate system kill.
-      sys.execute |= (EXEC_ALARM | EXEC_CRIT_EVENT); // Indicate hard limit critical event
+      bit_true(sys.execute, (EXEC_ALARM | EXEC_CRIT_EVENT)); // Indicate hard limit critical event
     }
   }
 }  
@@ -103,7 +103,7 @@ ISR(WDT_vect) // Watchdog timer ISR
       if (bit_istrue(settings.flags,BITFLAG_INVERT_LIMIT_PINS)) { bits ^= LIMIT_MASK; }
       if (bits & LIMIT_MASK) {
         mc_reset(); // Initiate system kill.
-        sys.execute |= (EXEC_ALARM | EXEC_CRIT_EVENT); // Indicate hard limit critical event
+        bit_true(sys.execute, (EXEC_ALARM | EXEC_CRIT_EVENT)); // Indicate hard limit critical event
       }
     }  
   }
@@ -238,7 +238,7 @@ void limits_go_home(uint8_t cycle_mask)
   // Initiate pull-off using main motion control routines. 
   // TODO : Clean up state routines so that this motion still shows homing state.
   sys.state = STATE_QUEUED;
-  sys.execute |= EXEC_CYCLE_START;
+  bit_true(sys.execute, EXEC_CYCLE_START);
   protocol_execute_runtime();
   protocol_buffer_synchronize(); // Complete pull-off motion.
   
@@ -259,7 +259,7 @@ void limits_soft_check(float *target)
       // workspace volume so just come to a controlled stop so position is not lost. When complete
       // enter alarm mode.
       if (sys.state == STATE_CYCLE) {
-        sys.execute |= EXEC_FEED_HOLD;
+        bit_true(sys.execute, EXEC_FEED_HOLD);
         do {
           protocol_execute_runtime();
           if (sys.abort) { return; }
@@ -267,7 +267,7 @@ void limits_soft_check(float *target)
       }
       
       mc_reset(); // Issue system reset and ensure spindle and coolant are shutdown.
-      sys.execute |= (EXEC_ALARM | EXEC_CRIT_EVENT); // Indicate soft limit critical event
+      bit_true(sys.execute, (EXEC_ALARM | EXEC_CRIT_EVENT)); // Indicate soft limit critical event
       protocol_execute_runtime(); // Execute to enter critical event loop and system abort
       return;
     

motion_control.c

@@ -288,13 +288,13 @@ void mc_probe_cycle(float *target, float feed_rate, uint8_t invert_feed_rate)
   // NOTE: Parser error-checking ensures the probe isn't already closed/triggered.
   sys.probe_state = PROBE_ACTIVE;
 
-  sys.execute |= EXEC_CYCLE_START;
+  bit_true(sys.execute, EXEC_CYCLE_START);
   do {
     protocol_execute_runtime(); 
     if (sys.abort) { return; } // Check for system abort
   } while ((sys.state != STATE_IDLE) && (sys.state != STATE_QUEUED));
 
-  if (sys.probe_state == PROBE_ACTIVE) { sys.execute |= EXEC_CRIT_EVENT; }
+  if (sys.probe_state == PROBE_ACTIVE) { bit_true(sys.execute, EXEC_CRIT_EVENT); }
   protocol_execute_runtime();   // Check and execute run-time commands
   if (sys.abort) { return; } // Check for system abort
 
@@ -316,7 +316,7 @@ void mc_probe_cycle(float *target, float feed_rate, uint8_t invert_feed_rate)
   mc_line(target, feed_rate, invert_feed_rate); // Bypass mc_line(). Directly plan homing motion.
   #endif
 
-  sys.execute |= EXEC_CYCLE_START;
+  bit_true(sys.execute, EXEC_CYCLE_START);
   protocol_buffer_synchronize(); // Complete pull-off motion.
   if (sys.abort) { return; } // Did not complete. Alarm state set by mc_alarm.
 
@@ -337,7 +337,7 @@ void mc_reset()
 {
   // Only this function can set the system reset. Helps prevent multiple kill calls.
   if (bit_isfalse(sys.execute, EXEC_RESET)) {
-    sys.execute |= EXEC_RESET;
+    bit_true(sys.execute, EXEC_RESET);
 
     // Kill spindle and coolant.   
     spindle_stop();
@@ -348,7 +348,7 @@ void mc_reset()
     // the steppers enabled by avoiding the go_idle call altogether, unless the motion state is
     // violated, by which, all bets are off.
     if (sys.state & (STATE_CYCLE | STATE_HOLD | STATE_HOMING)) {
-      sys.execute |= EXEC_ALARM; // Flag main program to execute alarm state.
+      bit_true(sys.execute, EXEC_ALARM); // Flag main program to execute alarm state.
       st_go_idle(); // Force kill steppers. Position has likely been lost.
     }
   }

nuts_bolts.h

@@ -44,9 +44,9 @@
 
 // Bit field and masking macros
 #define bit(n) (1 << n) 
-#define bit_true(x,mask) (x |= mask)
-#define bit_false(x,mask) (x &= ~mask)
-#define bit_toggle(x,mask) (x ^= mask)
+#define bit_true(x,mask) {uint8_t sreg = SREG; cli(); (x) |= (mask); SREG = sreg; }
+#define bit_false(x,mask) {uint8_t sreg = SREG; cli(); (x) &= ~(mask); SREG = sreg; }
+#define bit_toggle(x,mask) {uint8_t sreg = SREG; cli(); (x) ^= (mask); SREG = sreg; }
 #define bit_istrue(x,mask) ((x & mask) != 0)
 #define bit_isfalse(x,mask) ((x & mask) == 0)
 

probe.c

@@ -45,7 +45,7 @@ void probe_state_monitor()
     if (probe_get_state()) {
       sys.probe_state = PROBE_OFF;
       memcpy(sys.probe_position, sys.position, sizeof(float)*N_AXIS);
-      sys.execute |= EXEC_FEED_HOLD;
+      bit_true(sys.execute, EXEC_FEED_HOLD);
     }
   }
 }

protocol.c

@@ -288,4 +288,4 @@ void protocol_buffer_synchronize()
 // NOTE: This function is called from the main loop and mc_line() only and executes when one of
 // two conditions exist respectively: There are no more blocks sent (i.e. streaming is finished, 
 // single commands), or the planner buffer is full and ready to go.
-void protocol_auto_cycle_start() { if (sys.auto_start) { sys.execute |= EXEC_CYCLE_START; } } 
+void protocol_auto_cycle_start() { if (sys.auto_start) { bit_true(sys.execute, EXEC_CYCLE_START); } } 

serial.c

@@ -157,9 +157,9 @@ ISR(SERIAL_RX)
   // Pick off runtime command characters directly from the serial stream. These characters are
   // not passed into the buffer, but these set system state flag bits for runtime execution.
   switch (data) {
-    case CMD_STATUS_REPORT: sys.execute |= EXEC_STATUS_REPORT; break; // Set as true
-    case CMD_CYCLE_START:   sys.execute |= EXEC_CYCLE_START; break; // Set as true
-    case CMD_FEED_HOLD:     sys.execute |= EXEC_FEED_HOLD; break; // Set as true
+    case CMD_STATUS_REPORT: bit_true(sys.execute, EXEC_STATUS_REPORT); break; // Set as true
+    case CMD_CYCLE_START:   bit_true(sys.execute, EXEC_CYCLE_START); break; // Set as true
+    case CMD_FEED_HOLD:     bit_true(sys.execute, EXEC_FEED_HOLD); break; // Set as true
     case CMD_RESET:         mc_reset(); break; // Call motion control reset routine.
     default: // Write character to buffer    
       next_head = rx_buffer_head + 1;

system.c

@@ -46,9 +46,9 @@ ISR(PINOUT_INT_vect)
     if (bit_isfalse(PINOUT_PIN,bit(PIN_RESET))) {
       mc_reset();
     } else if (bit_isfalse(PINOUT_PIN,bit(PIN_FEED_HOLD))) {
-      sys.execute |= EXEC_FEED_HOLD; 
+      bit_true(sys.execute, EXEC_FEED_HOLD); 
     } else if (bit_isfalse(PINOUT_PIN,bit(PIN_CYCLE_START))) {
-      sys.execute |= EXEC_CYCLE_START;
+      bit_true(sys.execute, EXEC_CYCLE_START);
     } 
   }
 }