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bh=zNebPkkCATOz/8G2Ty+8PI8yqXvC2oGmbRAGfEPpIEQ=; b=BYufc599OW5+qnbK4980v4vs8tbQ87dmQIKHUIPm3bX0LdTh0yIimmqTGgpRF4pdPWiMQ/ 9atAPwy9bSVufVu+YVSgJRUcHYhyAZXzi70kAHjGnnew2XCIKo6bSYoarnmjAdCO8coEc+ nGYLJhoqUfmAsEP1lx4eG7K9Ilf00dKu7Y4/Wv8fktbDVILaQe2r8tZhjww40k8cslhg0+ vxwi/ZrPIiQuKFeSlDldo1u+YI/eJCpR28+wc0QfOP/DxCzgbjls4tyLRTIT1q6YwvvynM xzD5E20+n5g/hImN0kKjIE50A5ZLyfqcK3N4s46/l+BF23pdTEpg8rSLzjDZ/g== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1726573826; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=zNebPkkCATOz/8G2Ty+8PI8yqXvC2oGmbRAGfEPpIEQ=; b=0W9NCMyQ+egH0HM5V0+4TQQneA5B2GzQAI0DJcSHVUfp/Ie0VUkXoSOjbkPqE/A0+QEHRs mDGYjLCZ8ngz+7CA== To: Will Deacon , "Christoph Lameter (Ampere)" Cc: kernel test robot , Christoph Lameter via B4 Relay , Catalin Marinas , Peter Zijlstra , Ingo Molnar , Waiman Long , Boqun Feng , oe-kbuild-all@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-arch@vger.kernel.org, Jani Nikula , Rodrigo Vivi , intel-gfx@lists.freedesktop.org Subject: Re: [PATCH v3] Avoid memory barrier in read_seqcount() through load acquire In-Reply-To: <20240917073703.GB27290@willie-the-truck> References: <20240912-seq_optimize-v3-1-8ee25e04dffa@gentwo.org> <202409132135.ki3Mp5EA-lkp@intel.com> <766fe92a-13da-f299-0ecf-f8a477d58a79@gentwo.org> <20240917073703.GB27290@willie-the-truck> Date: Tue, 17 Sep 2024 13:50:25 +0200 Message-ID: <87r09i1ou6.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain X-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: B7467A0019 X-Stat-Signature: oeazmn6yqjphn5mn7791qafuesj51qo8 X-HE-Tag: 1726573828-711601 X-HE-Meta: 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 kECXYnEY h9At6R1gJli/aLALd5rtgLvb45fuGk8hO5LVoxJeE0R2Q4ZsJJwr5wfk5ARuAwKied2qUy5S/1UfriBiBQNpMWGDJLHARVFe6zJVHt/68ZeKNyFz0GFztvKEZz/WpQGHmDYvXfA52Su2/PIebp9cLfCE7E1LfjoGWgSOmlDRcHA73BSnM9icCG45sLp4TLkFLK0sP5GCX2qJCWmCXfMQTcRL/aNisLD/SxAGpjh8XZcUqwFjWa6CCz4yWW9HfEH9lNG1LStCImX2x2lnFBCqK3kBAKbCMPl0mz0gkHleCtziTd6APPD58RSoLi1k2+XwLt+1uuUR/eXZjvzOwgL2XhAp7CqhcXBkC0450kkgFshEcZbgGA0IjrD4qzZn1v/W51WOHkYStVBpaRiuE1hY29KQNHDgCXP2FMDFN X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Cc+ i915 people On Tue, Sep 17 2024 at 08:37, Will Deacon wrote: > On Mon, Sep 16, 2024 at 10:52:18AM -0700, Christoph Lameter (Ampere) wrote: >> On Fri, 13 Sep 2024, kernel test robot wrote: >> >> > >> drivers/gpu/drm/i915/gt/intel_tlb.h:21:47: error: macro "seqprop_sequence" requires 2 arguments, but only 1 given >> >> From 15d86bc9589f16947c5fb0f34d2947eacd48f853 Mon Sep 17 00:00:00 2001 >> From: Christoph Lameter >> Date: Mon, 16 Sep 2024 10:44:16 -0700 >> Subject: [PATCH] Update Intel DRM use of seqprop_sequence >> >> One of Intels drivers uses seqprop_sequence() for its tlb sequencing. >> We added a parameter so that we can use acquire. Its pretty safe to >> assume that this will work without acquire. >> >> Signed-off-by: Christoph Lameter >> --- >> drivers/gpu/drm/i915/gt/intel_tlb.h | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/gpu/drm/i915/gt/intel_tlb.h b/drivers/gpu/drm/i915/gt/intel_tlb.h >> index 337327af92ac..81998c4cd4fb 100644 >> --- a/drivers/gpu/drm/i915/gt/intel_tlb.h >> +++ b/drivers/gpu/drm/i915/gt/intel_tlb.h >> @@ -18,7 +18,7 @@ void intel_gt_fini_tlb(struct intel_gt *gt); >> >> static inline u32 intel_gt_tlb_seqno(const struct intel_gt *gt) >> { >> - return seqprop_sequence(>->tlb.seqno); >> + return seqprop_sequence(>->tlb.seqno, false); >> } > > Yikes, why is the driver using the seqlock internals here? It's a bit of > a pity, as a quick grep suggest that this is the _only_ user of > 'seqcount_mutex_t', yet it's still having to work around the API. Why the hell can't i915 use the proper interfaces and has to bypass the core code? Just because C allows that does not make it correct. Can the i915 people please remove this blatant violation of layering? Thanks, tglx