On 5/31/24 14:52, Konstantin Belousov wrote:
On Wed, May 22, 2024 at 05:37:56AM +0000, Kyle Evans wrote:
The branch main has been updated by kevans:
URL:
https://cgit.FreeBSD.org/src/commit/?id=6e824f3713011f7955a4f88fb16445e8e2cbe72c
commit 6e824f3713011f7955a4f88fb16445e8e2cbe72c
Author: Kyle Evans <kev...@freebsd.org>
AuthorDate: 2024-05-22 05:36:29 +0000
Commit: Kyle Evans <kev...@freebsd.org>
CommitDate: 2024-05-22 05:37:41 +0000
time: siginfo_recvd needs to be marked volatile
I do not think so. It happens to work with the compilers we currently use.
Sorry, I meant to respond but it got lost somewhere in the stack. Can
you expand on this specifically a bit more? I was under the impression
that we'd generally need volatility due to write from SIGINFO handler /
read repeatedly from main(), which serves to demonstrate my ignorance
here. Is it that there are sufficient side-effect-y things between
loads in the wait4() loop that the compiler won't do anything hinky, or
more that it's insufficient and should have been fenced as well?
sig_atomic_t does not imply volatility, we must do it ourselves to avoid
caching of siginfo_recvd loads.
For this purpose, standard provides atomic_signal_fence().
You would need to put it before read of siginfo_recvd (after wait4()), and
after update of siginfo_recvd in the signal handler.
