[Lldb-commits] [PATCH] D38938: Logging: provide a way to safely disable logging in a forked process

Zachary Turner via lldb-commits lldb-commits at lists.llvm.org
Mon Oct 16 13:57:19 PDT 2017

On Sun, Oct 15, 2017 at 3:15 PM Pavel Labath <labath at google.com> wrote:

> On 15 October 2017 at 23:04, Zachary Turner <zturner at 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:
logSomething();  // thread 2 forks when thread 1 is here.

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

As a follow-up question, why can't we use execve instead of fork / exec?
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