[Lldb-commits] [PATCH] D144311: [debugserver] Add one additional sleep before attaching after waiting

[Alex Langford via Phabricator via lldb-commits]

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It's possible for debugserver to attach to a process during the handoff
between /usr/lib/dyld and the dyld in the shared cache. When that
happens, we may end up in a state where there is no dyld in the process
and our debugging session is doomed. To make that scenario a lot less
likely, we can insert a sleep right before attaching after waiting to
find the right pid.

rdar://105513180


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D144311

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


Index: lldb/tools/debugserver/source/DNB.cpp
===================================================================
--- lldb/tools/debugserver/source/DNB.cpp
+++ lldb/tools/debugserver/source/DNB.cpp
@@ -793,6 +793,14 @@
   if (waitfor_pid != INVALID_NUB_PROCESS) {
     DNBLogThreadedIf(LOG_PROCESS, "Attaching to %s with pid %i...\n",
                      waitfor_process_name, waitfor_pid);
+    // In some cases, we attempt to attach during the transition from
+    // /usr/lib/dyld to the dyld in the shared cache. If that happens, we may
+    // end up in a state where there is no dyld in the process and from there
+    // the debugging session is doomed.
+    // In an attempt to make this scenario much less likely, we sleep
+    // for an additional `waitfor_interval` number of microseconds before
+    // attaching.
+    ::usleep(waitfor_interval);
     waitfor_pid = DNBProcessAttach(waitfor_pid, timeout_abstime,
                                    ctx->GetIgnoredExceptions(), err_str, 
                                    err_len);


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