This thread behavior over fork is the same on Mach, BTW. Apple extended posix_spawnp to take a “Stop at first instruction” attribute, basically just running PT_TRACEME for us. That has ended up being very handy because we get all the nice cleanup behavior that pthread_spawn does, but still get the one thing the debugger needs fork for… Don’t know whether it does something useful for locks, however.
Jim > On Oct 16, 2017, at 2:06 PM, Tamas Berghammer via lldb-commits > <lldb-commits@lists.llvm.org> wrote: > > On linux when you call fork the new process will only have the thread what > called fork. Other threads will be ignored with leaving whatever dirty state > they had left in the new process. Regarding execve it doesn't do fork so we > would have to do fork & execve what have the same issue (actually we are > using execve as of now but it isn't different from exec in this regard). > > Tamas > > On Mon, Oct 16, 2017 at 1:57 PM Zachary Turner via lldb-commits > <lldb-commits@lists.llvm.org <mailto:lldb-commits@lists.llvm.org>> wrote: > On Sun, Oct 15, 2017 at 3:15 PM Pavel Labath <lab...@google.com > <mailto:lab...@google.com>> wrote: > On 15 October 2017 at 23:04, Zachary Turner <ztur...@google.com > <mailto:ztur...@google.com>> wrote: > > Doesn’t DisableAllLogChannels acquire a scoped lock? If so wouldn’t it just > > release at the end of the function? > > > The thing is, it is unable to acquire the lock in the first place, > because the mutex is already "locked". So, the sequence of events is > process 1, thread 1: acquire lock > process 1, thread 2: fork(), process 2 is created > process 1 thread 1: release lock > > Suppose process 1 thread 1 had been executing this code: > ``` > lock(); > logSomething(); // thread 2 forks when thread 1 is here. > unlock(); > ``` > > Doesn't thread 2 in the child process resume running from the same point? If > so, it seems that both the child and parent would both gracefully unlock the > lock. > > I'm sure I'm wrong about this, but hopefully you can clarify what I'm missing. > > As a follow-up question, why can't we use execve instead of fork / exec? > _______________________________________________ > lldb-commits mailing list > lldb-commits@lists.llvm.org <mailto:lldb-commits@lists.llvm.org> > http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits > <http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits> > _______________________________________________ > lldb-commits mailing list > lldb-commits@lists.llvm.org > http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits
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