From nobody Sun Feb 8 06:54:10 2026 Received: from out-173.mta0.migadu.com (out-173.mta0.migadu.com [91.218.175.173]) (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 889662D0603 for ; Mon, 29 Dec 2025 06:34:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.173 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766990062; cv=none; b=A6ek9WiqaZUsfsoViQbKAe54HJswUWHUIIowI8fL36vIX29U3LAGwAfOz+ZJ68CYdfp4o4ZqsYp6xE0eCifLYWxynf9okF29Lk4n6r7ttm4w9MUpHRl44VpOzKvhybqIcUb7bUo7+egqwi4KEaQoJzrMgh0AXEf/N6jc1P+XQrc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766990062; c=relaxed/simple; bh=P+qofRHgKI9mEvf/M2+uRxs0vPJHcW9djs3JSnJOuKU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=M3ENqbVR7USa8qSr5pBUidr+DlWOM2dh1ktj/nfKPh1ydonZGDXoV3HpmWkpsDz2s5tbCgTuRSN8VVZubIMu0aVu5QrQpjLQBSfJNv99JKSlSLDKhk0ocSFzTSi59Dee8iqRxJ2PNnVhFs9DLrkrL43SZMhBTgXIYGuXQ6URzW0= 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=foB+0N8C; arc=none smtp.client-ip=91.218.175.173 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="foB+0N8C" 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=1766990058; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=9e1GeNzrkliZLlZL213Exbk9DDZDpepWNXJsRZoIj9M=; b=foB+0N8C+D/7YAJV4KSBB2eIaxqQZrJXHykBcuiCYbaj9itN8sCX2iACZztrxw43VdDhk7 jvi4KOYr1VJi96rTfB3BFpPdjnE60QYVe22nfvEZbKT6vX9MujUWd0jR3/CTEL4ixpo9Fk R5E/z6n37jIUfBpjYdOdZwuIeAsE6ng= From: George Guo To: hengqi.chen@gmail.com Cc: chenhuacai@kernel.org, dongtai.guo@linux.dev, guodongtai@kylinos.cn, kernel@xen0n.name, lianyangyang@kylinos.cn, linux-kernel@vger.kernel.org, loongarch@lists.linux.dev, r@hev.cc, xry111@xry111.site Subject: [PATCH loongarch-next 2/4] LoongArch: Add 128-bit atomic cmpxchg support Date: Mon, 29 Dec 2025 14:34:06 +0800 Message-ID: <20251229063408.34340-3-dongtai.guo@linux.dev> In-Reply-To: <20251229063408.34340-1-dongtai.guo@linux.dev> References: <20251229063408.34340-1-dongtai.guo@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Migadu-Flow: FLOW_OUT Content-Type: text/plain; charset="utf-8" From: George Guo Implement 128-bit atomic compare-and-exchange using LoongArch's LL.D/SC.Q instructions. At the same time, fix BPF scheduler test failures (scx_central scx_qmap) caused by kmalloc_nolock_noprof returning NULL due to missing 128-bit atomics. The NULL returns led to -ENOMEM errors during scheduler initialization, causing test cases to fail. Verified by testing with the scx_qmap scheduler (located in tools/sched_ext/). Building with `make` and running ./tools/sched_ext/build/bin/scx_qmap. Signed-off-by: George Guo --- arch/loongarch/include/asm/cmpxchg.h | 47 ++++++++++++++++++++++++++++ 1 file changed, 47 insertions(+) diff --git a/arch/loongarch/include/asm/cmpxchg.h b/arch/loongarch/include/= asm/cmpxchg.h index 0494c2ab553e..61ce6a0889f0 100644 --- a/arch/loongarch/include/asm/cmpxchg.h +++ b/arch/loongarch/include/asm/cmpxchg.h @@ -137,6 +137,44 @@ __arch_xchg(volatile void *ptr, unsigned long x, int s= ize) __ret; \ }) =20 +union __u128_halves { + u128 full; + struct { + u64 low; + u64 high; + }; +}; + +#define __cmpxchg128_asm(ptr, old, new) \ +({ \ + union __u128_halves __old, __new, __ret; \ + volatile u64 *__ptr =3D (volatile u64 *)(ptr); \ + \ + __old.full =3D (old); \ + __new.full =3D (new); \ + \ + __asm__ __volatile__( \ + "1: ll.d %0, %3 # 128-bit cmpxchg low \n" \ + __WEAK_LLSC_MB \ + " ld.d %1, %4 # 128-bit cmpxchg high \n" \ + " bne %0, %z5, 2f \n" \ + " bne %1, %z6, 2f \n" \ + " move $t0, %z7 \n" \ + " move $t1, %z8 \n" \ + " sc.q $t0, $t1, %2 \n" \ + " beqz $t0, 1b \n" \ + "2: \n" \ + __WEAK_LLSC_MB \ + : "=3D&r" (__ret.low), "=3D&r" (__ret.high) \ + : "r" (__ptr), \ + "ZC" (__ptr[0]), "m" (__ptr[1]), \ + "Jr" (__old.low), "Jr" (__old.high), \ + "Jr" (__new.low), "Jr" (__new.high) \ + : "t0", "t1", "memory"); \ + \ + __ret.full; \ +}) + static inline unsigned int __cmpxchg_small(volatile void *ptr, unsigned in= t old, unsigned int new, unsigned int size) { @@ -224,6 +262,15 @@ __cmpxchg(volatile void *ptr, unsigned long old, unsig= ned long new, unsigned int __res; \ }) =20 +/* cmpxchg128 */ +#define system_has_cmpxchg128() 1 + +#define arch_cmpxchg128(ptr, o, n) \ +({ \ + BUILD_BUG_ON(sizeof(*(ptr)) !=3D 16); \ + __cmpxchg128_asm(ptr, o, n); \ +}) + #ifdef CONFIG_64BIT #define arch_cmpxchg64_local(ptr, o, n) \ ({ \ --=20 2.49.0