[lldb-dev] Remote Non-Stop Mode

Ewan Crawford ewan at codeplay.com
Tue May 19 01:52:32 PDT 2015

Hi everybody,

We have implemented remote support for non-stop mode in a local Hexagon 
repo of LLDB and begun to upstream the work, see 
http://reviews.llvm.org/D9656. Non-Stop mode in a remote stub lets you 
examine a single stopped thread while others execute normally. This 
isn't currently a feature of llgs, but is of gdbserver and can be tested 
on x86.

The remote protocol currently needs to be extended to support 
asynchronous notifications so it can interact with a non-stop stub. To 
solve this we've switched to multi-threaded mode from the abstract 
communications class by implementing AppendBytesToCache() in 
GDBRemoteCommunication. Allowing us to spawn a read thread that 
continually reads packets into a packet queue. Packets are then accessed 
by popping a packet from the queue in a thread safe manner.

Since this is a significant change to the remote protocol implementation 
which won't just affect non-stop mode I'd like some feedback to check if 
people have any comments about it.

The patches are ready to go, and will be put up for review soon.


Ewan Crawford
Codeplay Software Ltd
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