cameron314 created this revision.
cameron314 added reviewers: clayborg, zturner, jingham.
cameron314 added subscribers: mamai, lldb-commits.
cameron314 set the repository for this revision to rL LLVM.
When stopping the private state thread, there was a race condition between the
time the thread exits (resetting the HostThread object) and the time a Join was
attempted, especially in the case of a timeout.
The previous workaround of copying the HostThread object is not enough, since
on a Reset the internal thread stuff gets nulled out regardless of which
HostThread object actually has Reset called on it, resulting in an attempt to
dereference a null pointer on the subsequent call to Join from the copy as well.
In our environment (custom target), we were hitting this every time we stopped
debugging.
Repository:
rL LLVM
http://reviews.llvm.org/D19122
Files:
source/Target/Process.cpp
Index: source/Target/Process.cpp
===================================================================
--- source/Target/Process.cpp
+++ source/Target/Process.cpp
@@ -4112,11 +4112,8 @@
if (log)
log->Printf ("Process::%s (signal = %d)", __FUNCTION__, signal);
- // Signal the private state thread. First we should copy this is case the
- // thread starts exiting since the private state thread will NULL this out
- // when it exits
- HostThread private_state_thread(m_private_state_thread);
- if (private_state_thread.IsJoinable())
+ // Signal the private state thread
+ if (m_private_state_thread.IsJoinable())
{
TimeValue timeout_time;
bool timed_out;
@@ -4134,7 +4131,7 @@
{
if (timed_out)
{
- Error error = private_state_thread.Cancel();
+ Error error = m_private_state_thread.Cancel();
if (log)
log->Printf ("Timed out responding to the control event,
cancel got error: \"%s\".", error.AsCString());
}
@@ -4145,7 +4142,7 @@
}
thread_result_t result = NULL;
- private_state_thread.Join(&result);
+ m_private_state_thread.Join(&result);
m_private_state_thread.Reset();
}
}
@@ -4449,7 +4446,6 @@
if (!is_secondary_thread)
m_public_run_lock.SetStopped();
m_private_state_control_wait.SetValue (true, eBroadcastAlways);
- m_private_state_thread.Reset();
return NULL;
}
Index: source/Target/Process.cpp
===================================================================
--- source/Target/Process.cpp
+++ source/Target/Process.cpp
@@ -4112,11 +4112,8 @@
if (log)
log->Printf ("Process::%s (signal = %d)", __FUNCTION__, signal);
- // Signal the private state thread. First we should copy this is case the
- // thread starts exiting since the private state thread will NULL this out
- // when it exits
- HostThread private_state_thread(m_private_state_thread);
- if (private_state_thread.IsJoinable())
+ // Signal the private state thread
+ if (m_private_state_thread.IsJoinable())
{
TimeValue timeout_time;
bool timed_out;
@@ -4134,7 +4131,7 @@
{
if (timed_out)
{
- Error error = private_state_thread.Cancel();
+ Error error = m_private_state_thread.Cancel();
if (log)
log->Printf ("Timed out responding to the control event, cancel got error: \"%s\".", error.AsCString());
}
@@ -4145,7 +4142,7 @@
}
thread_result_t result = NULL;
- private_state_thread.Join(&result);
+ m_private_state_thread.Join(&result);
m_private_state_thread.Reset();
}
}
@@ -4449,7 +4446,6 @@
if (!is_secondary_thread)
m_public_run_lock.SetStopped();
m_private_state_control_wait.SetValue (true, eBroadcastAlways);
- m_private_state_thread.Reset();
return NULL;
}
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