[Lldb-commits] [lldb] Send an explicit interrupt to cancel an attach waitfor. (PR #72565)

[Jason Molenda via lldb-commits]

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@@ -799,7 +799,33 @@ DNBProcessAttachWait(RNBContext *ctx, const char *waitfor_process_name,
         break;
       }
 
-      ::usleep(waitfor_interval); // Sleep for WAITFOR_INTERVAL, then poll again
+      // Now we're going to wait a while before polling again.  But we also
+      // need to check whether we've gotten an event from the debugger  
+      // telling us to interrupt the wait.  So we'll use the wait for a possible
+      // next event to also be our short pause...
+      struct timespec short_timeout;
+      DNBTimer::OffsetTimeOfDay(&short_timeout, 0, waitfor_interval);
+      uint32_t event_mask = RNBContext::event_read_packet_available 
+          | RNBContext::event_read_thread_exiting;
+      nub_event_t set_events = ctx->Events().WaitForSetEvents(event_mask, 
+          &short_timeout);
+      if (set_events & RNBContext::event_read_packet_available) {
+        // If we get any packet from the debugger while waiting on the async,
+        // it has to be telling us to interrupt.  So always exit here.
+        // Over here in DNB land we can see that there was a packet, but all
+        // the methods to actually handle it are protected.  It's not worth
+        // rearranging all that just to get which packet we were sent...
+        DNBLogError("Interrupted by packet while waiting for '%s' to appear.\n",
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jasonmolenda wrote:

The structure of the gdb remote protocol is such that when you've sent a packet, you can't send anything else until you get a response.  "continue" is special in that you can send ^C to the remote stub to interrupt execution.  A "waitfor" attach request most reasonably behaves the same as "continue" - the only thing it would make any sense for the debugger to send when we're waiting is ^C.  If the debugger were to send anything else, yeah, something has gone very wrong, but when Jim described the layering and how it wasn't straightforward to check that, I didn't push further, it seemed fine to me to assume the debugger didn't do something unsupported like send a non-interrupt packet.

https://github.com/llvm/llvm-project/pull/72565