[Lldb-commits] [PATCH] D158035: [lldb] Protect RNBRemote from a data race

[Augusto Noronha via Phabricator via lldb-commits]

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Thread sanitizer reports the following data race:

  Write of size 8 at 0x000103303e70 by thread T1 (mutexes: write M0):
    #0 RNBRemote::CommDataReceived(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>> const&) RNBRemote.cpp:1075 (debugserver:arm64+0x100038db8) (BuildId: f130b34f693c4f3eba96139104af2b7132000000200000000100000000000e00)
    #1 RNBRemote::ThreadFunctionReadRemoteData(void*) RNBRemote.cpp:1180 (debugserver:arm64+0x1000391dc) (BuildId: f130b34f693c4f3eba96139104af2b7132000000200000000100000000000e00)
  
  Previous read of size 8 at 0x000103303e70 by main thread:
    #0 RNBRemote::GetPacketPayload(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>&) RNBRemote.cpp:797 (debugserver:arm64+0x100037c5c) (BuildId: f130b34f693c4f3eba96139104af2b7132000000200000000100000000000e00)
    #1 RNBRemote::GetPacket(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>&, RNBRemote::Packet&, bool) RNBRemote.cpp:907 (debugserver:arm64+0x1000378cc) (BuildId: f130b34f693c4f3eba96139104af2b7132000000200000000100000000000e00)

RNBRemote already has a mutex, extend its usage to protect the read of
m_rx_packets.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D158035

Files:
  lldb/tools/debugserver/source/RNBRemote.cpp


Index: lldb/tools/debugserver/source/RNBRemote.cpp
===================================================================
--- lldb/tools/debugserver/source/RNBRemote.cpp
+++ lldb/tools/debugserver/source/RNBRemote.cpp
@@ -792,12 +792,12 @@
   // m_rx_packets.size());
   return_packet.swap(m_rx_packets.front());
   m_rx_packets.pop_front();
-  locker.Reset(); // Release our lock on the mutex
 
   if (m_rx_packets.empty()) {
     // Reset the remote command available event if we have no more packets
     m_ctx.Events().ResetEvents(RNBContext::event_read_packet_available);
   }
+  locker.Reset(); // Release our lock on the mutex
 
   // DNBLogThreadedIf (LOG_RNB_MEDIUM, "%8u RNBRemote::%s: '%s'",
   // (uint32_t)m_comm.Timer().ElapsedMicroSeconds(true), __FUNCTION__,


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