Re: [PATCH v1 2/2] mm/memory-failure: send SIGBUS(BUS_MCEERR_AR) only to current thread

["HORIGUCHI NAOYA(堀口 直也)" <naoya.horiguchi@nec.com>]

On Mon, Jun 08, 2020 at 03:17:59PM -0700, Luck, Tony wrote:
> On Fri, Jun 05, 2020 at 10:37:19AM +0900, Naoya Horiguchi wrote:
> > Action Required memory error should happen only when a processor is
> > about to access to a corrupted memory, so it's synchronous and only
> > affects current process/thread.  Recently commit 872e9a205c84 ("mm,
> > memory_failure: don't send BUS_MCEERR_AO for action required error")
> > fixed the issue that Action Required memory could unnecessarily send
> > SIGBUS to the processes which share the error memory. But we still have
> > another issue that we could send SIGBUS to a wrong thread.
> > 
> > This is because collect_procs() and task_early_kill() fails to add the
> > current process to "to-kill" list.  So this patch is suggesting to fix
> > it.  With this fix, SIGBUS(BUS_MCEERR_AR) is never sent to non-current
> > process/thread.
> 
> Does the new code now send SIGBUS(BUS_MCEERR_AO) to all the other threads
> of a multi-threaded process?

No, it doesn't. This patch should not change anything for Action Optional
case, and find_early_kill_thread() chooses one thread per process, so
SIGBUS(BUS_MCEERR_AO) (as well as SIGBUS(BUS_MCEERR_AR)) should be sent only
to the chosen thread.

- Naoya

> 
> It looks like it might (and I don't have some handy multi-threaded test
> case to try it out).
> 
> If it does, is that what we want?
> 
> -Tony
>