[lldb-dev] More linux process control and IOHandler races

Matthew Gardiner mg11 at csr.com
Fri Aug 8 00:24:39 PDT 2014

Shawn Best wrote:
> Hi Matthew,
> I think the other stops are perfectly normal.  There are cases where 
> the inferior program will temporarily stop (for example waiting to 
> load dependent libraries, or maybe stepping over multiple instructions 
> in a section of code).  In these 'private stop' cases, it is 
> determined the stop is temporary and it will quietly restart the program.

For a "program launch" where the user does not want to stop at the 
inferior's entry point, then only 1 stop should occur. Compile the 
program I've attached, in linux, it launches a program (/bin/ls - which 
has shared library dependencies on my system) with a tracer and wait for 
stops. Perhaps there's good reason for the other 2 stops when lldb is 
the debugger, I'm just unaware of them right now.

Jim Ingham, I think may be alluding to other reasons why we see 3 stops 
on "program launch" in his mail on this thread, but I've not digested 
that mail thoroughly yet.

> In the case where the program is meant to stop (i.e. hitting a 
> breakpoint) the event is broadcast so the state machine in 
> HandleProcessEvents picks it up and changes the public state to stop, 
> dumps some information and pops the IOHandler so the user can interact 
> with the command line.

Yeah, agreed.
> I went through the same steps as you chasing this problem.  I also 
> stepped through the equivalent code on OSX, which does it completely 
> different and bypasses this issue.

Ok, fair enough. I don't know the differences between OSX and linux, or 
why as you say, a completely different flow happens which avoids our 
current problem.


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