On Fri, Oct 27, 2017 at 04:24:08PM -0700, Paul E. McKenney wrote:
> On Sat, Oct 28, 2017 at 12:18:47AM +0900, Akira Yokosawa wrote:
> > On 2017/10/27 18:33, Yubin Ruan wrote:
> > > And here are some more modification to some wording in chapter 7, but I am not
> > > sure whether you like it or not.
> > >
> > > Anyway, chapter 7 makes me feel good ;-) It makes me know that home-brewing a
> > > lock primitives with atomic instructions(which is what I was doing) is
> > > something that is possible and used in production.
> > >
> > > Thanks,
> > > Yubin
> > >
> > > diff --git a/locking/locking.tex b/locking/locking.tex
> > > index 14db27d..a9f46f1 100644
> > > --- a/locking/locking.tex
> > > +++ b/locking/locking.tex
> > > @@ -2166,8 +2166,8 @@ Signal-handler deadlocks can be explicitly avoided as follows:
> > > of a signal handler.
> > > \item If the application invokes the library function
> > > while holding a lock acquired within a given signal
> > > - handler, then that signal must be blocked every time that the
> > > - library function is called outside of a signal handler.
> > > + handler, then that signal must be blocked every time that lock
> > > + is to be acquired outside of a signal handler.
> >
> > The talking point here is library function and signal handler. So something like:
> >
> > + handler, then that signal must be blocked every time that one
> > + of related library functions is called outside of the signal handler.
> >
> > Thoughts?
>
> I believe that the major problem is that I didn't really specify the
> situation and constraints. How about the following?
>
> Thanx, Paul
>
> -----------------------------------------------------------------------
>
> commit 85025eaceff8cf10c9b674ba70d33dbd012e27ce
> Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
> Date: Fri Oct 27 16:21:33 2017 -0700
>
> locking: Clarify explicit avoidance of signal-handler deadlocks
>
> Reported-by: Yubin Ruan <ablacktshirt@xxxxxxxxx>
> Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
>
> diff --git a/locking/locking.tex b/locking/locking.tex
> index 14db27d1148b..025320b294ed 100644
> --- a/locking/locking.tex
> +++ b/locking/locking.tex
> @@ -2157,7 +2157,17 @@ locks, the strategies in the next section may prove helpful.
> \subsubsection{Explicitly Avoid Signal-Handler Deadlocks}
> \label{sec:locking:Explicitly Avoid Signal-Handler Deadlocks}
>
> -Signal-handler deadlocks can be explicitly avoided as follows:
> +Suppose that a given library function is known to acquire locks,
> +but does not block signals.
> +Suppose further that it is necessary to invoke that function both from
> +within and outside of a signal handler, and that it is not permissible
> +to modify this library function.
> +Of course, if no special action is taken, then if a signal arrives
> +while that library function is holding its lock, deadlock can occur
> +when the signal handler invokes that same library function,
> +which in turn attempts to re-acquire that same lock.
> +
> +Such deadlocks can be avoided as follows:
>
> \begin{enumerate}
> \item If the application invokes the library function from
>
These all look good to me. Thank you Paul.
Yubin
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