From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 080F952F264; Wed, 23 Sep 2026 14:27:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790173640; cv=none; b=cFHlfgp4U+RBuStUEGBHPEH27MUW9BISN2YYpocbBZohSOSJ0rfGsdMckc6ieDwjlGQtaTPNYQ+NAoXYYcFw6l0TvpzPOPD69Q9inSy/9u/62UapFyjNO3mL1f7RbjfSAHUZHCX/jkDFRAwQFopaGjx5eh1IBZdqYH8HctgOhQw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790173640; c=relaxed/simple; bh=nbrFKADTopHC8KXOMvl/u5dstQ6s95DvyBPbdQZY/ls=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=GuXOStsUXCAHnjyk7JjaQxIWiAt4INt/p/WZUx3cwCrwF9WTCMOB9m5eCc7Immefe8U0WfQn3NmBGBxD+r2XK5HyYEraWEaddc4tG18fgo7DfwboMeJ1yl348feFVM4628kRmowkmDl8VRammOg4G71zLK4MeGTHYNsmkHI7TVU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=jWJXdA2T; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="jWJXdA2T" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 32D331F000FF; Wed, 23 Sep 2026 14:27:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790173638; bh=8RZySu5ewO7OsL5+/SX5EiN9KyoUZH9ozgxibJKBDw0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=jWJXdA2T8dzgAwbGmunaSDBfTRg7AZIp2p2x7tXbHeDJMim/GZgpDJWXqYWndQsJ0 RYNvRiTov4PJKkvR7Qf9MUM32TcFo32yFJkMiWtkhhd0eWQsctnULYZqTJixoJLm16 uJL2ECOBlf+4uAbgWVNlimYAKTjACE2aours6aJ4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, =?UTF-8?q?Th=C3=A9o=20Lebrun?= , Jiaxun Yang , Thomas Bogendoerfer Subject: [PATCH 7.2 310/438] mips: select CONFIG_WEAK_REORDERING_BEYOND_LLSC from CONFIG_EYEQ Date: Wed, 23 Sep 2026 16:05:31 +0200 Message-ID: <20260923140652.811210400@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260923140644.756254324@linuxfoundation.org> References: <20260923140644.756254324@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 7.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Théo Lebrun commit bbc448c541ed90d52f9ec22f17394304e3bf170e upstream. On I6500 CPU cores, lld and scd give no ordering guarantees (same as all other instructions). To respect the assumption that arch_cmpxchg() is fully ordered, we must inject sync instructions above and below our lld/scd loops using the already in place WEAK_REORDERING_BEYOND_LLSC infrastructure. Otherwise, bad things can happen: [ 34.054496] CPU 3 Unable to handle kernel paging request at virtual address 0000000000000000, epc == a80000080838e01c, ra == a80000080838dfc4 [ 34.054559] Oops[#1]: [ 34.069561] CPU: 3 UID: 0 PID: 170 Comm: pipe_race Not tainted 7.2.0-rc6-01553-gb73c35220968-dirty #103 VOLUNTARY [ 34.079932] Hardware name: Mobile EyeQ5 MP5 Evaluation board [ 34.085592] $ 0 : 0000000000000000 0000000000000001 0000000000000000 0000000000000000 [ 34.093616] $ 4 : a800000808ee2618 000000000b7a879d 0000000000001000 0000000000000000 [ 34.101638] $ 8 : 0000000000e3f2c9 0000000000000000 a800000808a2a9f8 0000000000000000 [ 34.109660] $12 : a8000008139ffcd8 ffffffff84080018 a80000080837fae0 7878787878787878 [ 34.117682] $16 : a800000807e82940 0000000000001000 0000000000000000 0000000000000000 [ 34.125704] $20 : a800000802920e00 a8000008139ffdf8 a800000802649400 0000000000e3f2c9 [ 34.133726] $24 : 0000000000000006 00000001200406e0 [ 34.141783] $28 : a8000008139fc000 a8000008139ffd10 0000000000e3f2c8 a80000080838dfc4 [ 34.149837] epc : a80000080838e01c anon_pipe_read+0xd4/0x428 [ 34.155697] ra : a80000080838dfc4 anon_pipe_read+0x7c/0x428 [ 34.161549] Status: 140000e3 KX SX UX KERNEL EXL IE [ 34.166551] Cause : 40800408 (ExcCode 02) [ 34.170574] BadVA : 0000000000000000 [ 34.174161] PrId : 0001b028 (MIPS I6500) [ 34.178183] Process pipe_race (pid: 170, threadinfo=000000005ca35720, task=00000000e1013890, tls=000000014ebbb780) [ 34.188568] Stack : a800000802649400 0000000000000000 0000000000000000 a8000008139ffdd0 [ 34.196623] 0000000000000fba a800000808ee0000 0000000000000001 a8000008130c3e80 [ 34.204676] a8000008080d1280 a8000008139ffd58 a8000008139ffd58 1dbd2b22ea1dd500 [ 34.212729] a800000802649400 a800000808ee0000 ffffffffffffffea 0000000000000001 [ 34.220783] 0000000000001000 0000000000000000 00000001200ae518 ffffffffffffffff [ 34.228836] 000000fffbe0e530 a80000080837edf4 000000fffbe0e530 0000000000000000 [ 34.236890] 0000000000000000 0000000000000000 000000014ebb55a0 0000000000001000 [ 34.244943] 0000000000000001 a800000802649400 0000000000000000 0000000000000000 [ 34.252996] 0000000000000000 0000400400000000 0000000000000000 1dbd2b22ea1dd500 [ 34.261049] 00000000140000e3 a800000802649400 a800000802649400 a800000808ee0000 [ 34.269103] ... [ 34.271568] Call Trace: [ 34.274026] [] anon_pipe_read+0xd4/0x428 [ 34.279533] [] vfs_read+0x25c/0x318 [ 34.284607] [] ksys_read+0x104/0x138 [ 34.289763] [] syscall_common+0x44/0x68 [ 34.295187] [ 34.296689] Code: f84000cf 02209825 de020010 d8400004 02002825 0040f809 02802025 f84000c3 [ 34.306504] [ 34.308099] ---[ end trace 0000000000000000 ]--- My initial reproducer was the xdp-tools test suite. A standalone reproducer would be an lld/scd loop that, when the read is reordered by the CPU, triggers a fault. We can achieve this from userspace by stressing an anonymous pipe, which uses a mutex. Program used: // SPDX-License-Identifier: GPL-2.0 // pipe_race.c - reproducer for MIPS LL/SC reordering vs fs/pipe.c // // Two userspace processes on an anonymous pipe: // parent = writer: tight write() loop // child = reader: tight read() loop #define _GNU_SOURCE #include #include #include #include #include #include #include #include #include #include #include int main(void) { long wrsize = 70; // bytes per write() long rdsize = 4096; // bytes per read() int pfd[2]; char *buf; pid_t pid; int ret; ret = pipe(pfd); assert(!ret); pid = fork(); assert(pid >= 0); if (pid == 0) { /* reader */ close(pfd[1]); buf = malloc(rdsize); assert(buf); for (;;) { ssize_t n = read(pfd[0], buf, rdsize); if (n < 0 && errno == EINTR) continue; if (n <= 0) _exit(n < 0 ? 1 : 0); } } close(pfd[0]); /* writer */ buf = malloc(wrsize); assert(buf); memset(buf, 'x', wrsize); for (;;) { ssize_t n = write(pfd[1], buf, wrsize); if (n < 0 && errno == EINTR) continue; if (n != wrsize) break; } kill(pid, SIGKILL); wait(NULL); return 0; } Fixes: fbe0fae601b7 ("MIPS: mobileye: Add EyeQ6H support") Cc: stable@vger.kernel.org Signed-off-by: Théo Lebrun Reviewed-by: Jiaxun Yang Signed-off-by: Thomas Bogendoerfer Signed-off-by: Greg Kroah-Hartman --- arch/mips/Kconfig | 1 + 1 file changed, 1 insertion(+) --- a/arch/mips/Kconfig +++ b/arch/mips/Kconfig @@ -659,6 +659,7 @@ config EYEQ select USB_UHCI_BIG_ENDIAN_MMIO if CPU_BIG_ENDIAN select USE_OF select HOTPLUG_PARALLEL if HOTPLUG_CPU + select WEAK_REORDERING_BEYOND_LLSC help Select this to build a kernel supporting EyeQ SoC from Mobileye.