From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-180.mta0.migadu.com (out-180.mta0.migadu.com [91.218.175.180]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7263F3081A2 for ; Wed, 26 Nov 2025 02:06:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.180 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764122770; cv=none; b=Fi4HoUGC5blkVn97qjIVYbNIPJiAl6ffALt2yUbEL0BlVDP6EwKSo6axSLmno4nWocZswj8AIcoP+pxALQqOAfbyytS7Tvh2syLw3Nj55YyO1bKYQVyOXqEaeUn/+jZJEvVv+cG+DRfUM5Ev8fB6I5IIr0dl5nV1MeqR1LudYSg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764122770; c=relaxed/simple; bh=RyAId0GM4YN0ArTmhHUKslKPznhLpV8Z15TRDwNgIi8=; h=From:Subject:Date:Message-Id:MIME-Version:Content-Type:To:Cc; b=IxZnGNESzrCeDf8p9jSdFshPT6+5l6BKEsbHvFF1HAjxuL9lmNcDzzxUuaFB9VX+fsMKEG1y9pdZdE85S1N4T+XsVSTpL8HPxBNxuybfrTgYf+C6vXt8ISyNrhJhbEXgOe3oMwiW4Up4qjAJ4BACv9k4rTWrL+Ew8ZFO/db154E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=wh1foxUw; arc=none smtp.client-ip=91.218.175.180 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="wh1foxUw" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1764122762; 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: content-transfer-encoding:content-transfer-encoding; bh=EJ/Ue5Qky2MtwQsGNeb6W8oWcDHKfS+NJnISi7Fqbec=; b=wh1foxUwpvUFW06sb6lX2q8JNoYsnZ8Y4AqLkF1tXKThDtjs15debHalFusl8gQfnTSh68 per6vLxql+jl9SPUSLdISiyCh5EtMR516sUbcwhNzMX/xNJVYedYk1+pVtstq34KxZxcb+ JLGGgs5jqHKZIXDUH9vMY9jZ4+mxDF4= From: George Guo Subject: [PATCH v3 0/2] LoongArch: Add 128-bit atomic cmpxchg support (v3) Date: Wed, 26 Nov 2025 10:05:49 +0800 Message-Id: <20251126-2-v3-0-851b5a516801@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-B4-Tracking: v=1; b=H4sIAH1gJmkC/03MwQ6CMAzG8VchPTvTFYboyfcwHhwr0sSA2XTBk L27GyeO/6a/b4XAXjjApVrBc5Qg85SjPlTQj4/pyUpcbiAkozWhIuWw7lqy1A+tg/z39jzIsm3 c7rlHCZ/Z/7bJqMt1r6NWqE5orOubBo3B60um73J0HKHoSHvRFEFZ2Loj3TKZwZ33IqX0B30Zh RTEAAAA X-Change-ID: 20251120-2-d03862b2cf6d To: Huacai Chen , WANG Xuerui Cc: loongarch@lists.linux.dev, linux-kernel@vger.kernel.org, George Guo , George Guo X-Developer-Signature: v=1; a=ed25519-sha256; t=1764122759; l=2402; i=dongtai.guo@linux.dev; s=20251103; h=from:subject:message-id; bh=RyAId0GM4YN0ArTmhHUKslKPznhLpV8Z15TRDwNgIi8=; b=dOheip3SDPcVyZXvBgHYRdE4Adfy/snvPf2qQ3yFLrTTkFXBghMMt4ZHi7g/ceSG8K2fVRCnA WPi7bnE6fcXBWVwhDheDzsvtlPuQs7NxFoYofikYL87d9A/prcCaKNZ X-Developer-Key: i=dongtai.guo@linux.dev; a=ed25519; pk=yHUJPGx/kAXutP/NSHpj7hWW0KQNlv3w9H6ju4qUoTM= X-Migadu-Flow: FLOW_OUT This patch series adds 128-bit atomic compare-and-exchange support for LoongArch architecture, which fixes BPF scheduler test failures caused by missing 128-bit atomics support. The series consists of two patches: 1. "LoongArch: Add 128-bit atomic cmpxchg support" - Implements 128-bit atomic compare-and-exchange using LoongArch's LL.D/SC.Q instructions - Fixes BPF scheduler test failures (scx_central scx_qmap) where kmalloc_nolock_noprof returns NULL due to missing 128-bit atomics, leading to -ENOMEM errors during scheduler initialization 2. "LoongArch: Enable 128-bit atomics cmpxchg support" - Adds select HAVE_CMPXCHG_DOUBLE and select HAVE_ALIGNED_STRUCT_PAGE in Kconfig to enable 128-bit atomic cmpxchg support The issue was identified through BPF scheduler test failures where scx_central and scx_qmap schedulers would fail to initialize. Testing was performed using the scx_qmap scheduler from tools/sched_ext/, confirming that the patches resolve the initialization failures. Signed-off-by: George Guo --- Changes in v3: - dbar 0 -> __WEAK_LLSC_MB - =ZB" (__ptr[0]) -> "r" (__ptr) - Link to v2: https://lore.kernel.org/r/20251124-2-v2-0-b38216e25fd9@linux.dev Changes in v2: - Use a normal ld.d for the high word instead of ll.d to avoid race condition - Insert a dbar between ll.d and ld.d to prevent reordering - Simply __cmpxchg128_asm("ll.d", "sc.q", ptr, o, n) to __cmpxchg128_asm(ptr, o, n) - Fix address operand constraints after testing different approaches: * ld.d with "m" * ll.d with "ZC", * sc.q with "ZB"(alternative constraints caused issues: - "r" caused system hang - "ZC" caused compiler error: {standard input}: Assembler messages: {standard input}:10037: Fatal error: Immediate overflow. format: u0:0 ) - Link to v1: https://lore.kernel.org/r/20251120-2-v1-0-705bdc440550@linux.dev --- George Guo (2): LoongArch: Add 128-bit atomic cmpxchg support LoongArch: Enable 128-bit atomics cmpxchg support arch/loongarch/Kconfig | 2 ++ arch/loongarch/include/asm/cmpxchg.h | 47 ++++++++++++++++++++++++++++++++++++ 2 files changed, 49 insertions(+) --- base-commit: d5ae5ac32615e4af729f0610fdc11ff4f4798aef change-id: 20251120-2-d03862b2cf6d Best regards, -- George Guo