From: Peter Zijlstra <peterz@infradead.org>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Robin Murphy <robin.murphy@arm.com>,
Joerg Roedel <joro@8bytes.org>, Will Deacon <will@kernel.org>,
linux-kernel@vger.kernel.org, iommu@lists.linux.dev,
Randy Dunlap <rdunlap@infradead.org>,
"Paul E. McKenney" <paulmck@kernel.org>
Subject: Re: [PATCH] iommu: Convert unreachable() to BUG()
Date: Wed, 2 Apr 2025 09:52:09 +0200 [thread overview]
Message-ID: <20250402075209.GR5880@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <6zzyjtvkqc4ipj7ngtkx3jithfwpwuxlix677urlehgdnljwbl@wfoa5futari6>
On Tue, Apr 01, 2025 at 05:50:32PM -0700, Josh Poimboeuf wrote:
> On Thu, Mar 27, 2025 at 01:37:18PM +0100, Peter Zijlstra wrote:
> > On Wed, Mar 26, 2025 at 10:28:46PM -0700, Josh Poimboeuf wrote:
> > > Bare unreachable() should be avoided as it generates undefined behavior,
> > > e.g. falling through to the next function. Use BUG() instead so the
> > > error is defined.
> >
> > Right; I did a pass like this a while ago and thought I'd removed all
> > unreachable() abuse.
>
> Any reason not to just "#define unreachable() BUG()" and convert UD2 and
> similar to use __builtin_unreachable()?
Just remove unreachable() entirely at that point. But you're going to
have to update all the various arch code that does use it correctly :/
There are a few sites besides BUG() that need it; eg, long jumps when
bootstrapping etc.
But basically nothing outside of arch code should ever need or want
unreachable.
next prev parent reply other threads:[~2025-04-02 7:52 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-03-27 5:28 [PATCH] iommu: Convert unreachable() to BUG() Josh Poimboeuf
2025-03-27 12:37 ` Peter Zijlstra
2025-04-02 0:50 ` Josh Poimboeuf
2025-04-02 7:52 ` Peter Zijlstra [this message]
2025-03-27 13:00 ` Jason Gunthorpe
2025-03-27 14:58 ` Paul E. McKenney
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