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Thu, 15 Oct 2026 05:45:20 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ThreadId: AZUAoEL-p1MZ Date: Thu, 15 Oct 2026 11:45:00 +0200 From: "Arnd Bergmann" To: "John Paul Adrian Glaubitz" , "Ramin Moussavi" , "Andreas Larsson" , "David S . Miller" Cc: "Thomas Gleixner" , "Peter Zijlstra" , "Guenter Roeck" , sparclinux@vger.kernel.org, linux-kernel@vger.kernel.org, "Imre Kaloz" Message-Id: <6ee3bd4f-3563-4e14-a665-df1f766e4710@app.fastmail.com> In-Reply-To: References: <20261015085545.3246951-1-ramin.moussavi@yacoub.de> <20261015085545.3246951-4-ramin.moussavi@yacoub.de> <7334b77c-2ec7-4678-8296-f187e0304f49@app.fastmail.com> Subject: Re: [PATCH 3/4] sparc32: implement futex atomics, with casa detected at run time Content-Type: text/plain Content-Transfer-Encoding: 7bit On Thu, Oct 15, 2026, at 11:28, John Paul Adrian Glaubitz wrote: > On Thu, 2026-10-15 at 11:23 +0200, Arnd Bergmann wrote: >> On Thu, Oct 15, 2026, at 10:55, Ramin Moussavi wrote: >> > sparc32 has no futex_atomic_cmpxchg_inatomic() or >> > arch_futex_atomic_op_inuser() of its own. The generic versions only >> > work on UP, so FUTEX depends on !(SPARC32 && SMP) and an SMP kernel >> > has no futexes at all; NPTL cannot run on it. >> >> I believe there are existing patches for LEON with CASA that >> should just be merged, I would not worry about supporting broken >> CPUs that never had this. > > I think you mean the series by Imre Kaloz [1]? If yes, he actually > implements CASA emulation unless I'm missing something. No, I had not seen that one, I was actually surprised that Andreas never merged it as we had discussed this years ago when I looked at the Leon downstream kernel. I see it is still part of his downstream patches at [1], at least the versions from 4.9 to the latest (6.13). Arnd [1] https://download.gaisler.com/anonftp/linux/linux-2.6/kernel/