linux-kernel - Re: [PATCH] arm: always update thread

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Message-ID: <20181126234111.GA30658@n2100.armlinux.org.uk>
Date:   Mon, 26 Nov 2018 23:41:11 +0000
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     Rafael David Tinoco <rafael.tinoco@...aro.org>
Cc:     Vladimir Murzin <vladimir.murzin@....com>,
        Vincent Whitchurch <vincent.whitchurch@...s.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Timothy E Baldwin <T.E.Baldwin99@...bers.leeds.ac.uk>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] arm: always update thread_info->syscall

On Mon, Nov 26, 2018 at 11:33:03PM +0000, Russell King - ARM Linux wrote:
> On Mon, Nov 26, 2018 at 08:53:35PM -0200, Rafael David Tinoco wrote:
> > Right now, only way for task->thread_info->syscall to be updated is if
> > if _TIF_SYSCALL_WORK is set in current's task thread_info->flags
> > (similar to what has_syscall_work() checks for arm64).
> > 
> > This means that "->syscall" will only be updated if we are tracing the
> > syscalls through ptrace, for example. This is NOT the same behavior as
> > arm64, when pt_regs->syscallno is updated in the beginning of svc0
> > handler for *every* syscall entry.
> 
> So when was it decided that the syscall number will always be required
> (we need it to know how far back this has to be backported).

PS, I rather object to the fact that the required behaviour seems to
change, arch maintainers aren't told about it until... some test is
created at some random point in the future which then fails.

Surely there's a better way to communicate changes in requirements
than discovery-by-random-bug-report ?

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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