From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 1A49423ED5B; Fri, 9 Jan 2026 12:12:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767960766; cv=none; b=sVl2cDa9FWR6TVnj9KjUSjhcExYPVqT6ImvzELHz9mhu2jA9DT0zGlYXXdcVCAHxddkz6habYQcVRh8mEIsH0I4FydSTSZrM09zTs2Xn2vOh0sPfofzz7T+feTsPP7swLIglXzsoDn7m9XtaIGXs5cwe8RDwelesEIAnIpui3Rc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767960766; c=relaxed/simple; bh=56540hn6YH3BTW7lY5Vrs0TwZ8EndUh6bNwbpsd6VTc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Rervb8xhj8xDfDx+ZpAd+9i1oEAiIRHf8kMql40f2TGMxE/bgFEJHhK1tIRoKUiTFWm4Vcf/0Hw6Qbo5pxoEBf7oBjDDMY0MzcphnmOcuWc2y3h6hWbquj17CipF1r/470nwSm9IRCH+4pzXz3HKr+NxOxP82cnQsCyrwOYoI3k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=N6i/S/zJ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="N6i/S/zJ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 60256C4CEF1; Fri, 9 Jan 2026 12:12:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1767960765; bh=56540hn6YH3BTW7lY5Vrs0TwZ8EndUh6bNwbpsd6VTc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=N6i/S/zJua9AExPBKPIpbAPpxJmZlAq9/soJfMItrjSZrsSeyUwDCGZDZVj2lBSxk xYMekMBqXAOpDRUeDhRwCwJapvBMtIg/qIpSkW/3RrpcEVprRCeoEiPNokP2l67sY7 4woUVeCy9klLnKf87o3hYfDvFt/ozIhaIJMbq3DE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Yeoreum Yun , Simon Horman , Paolo Abeni , Sasha Levin Subject: [PATCH 6.6 517/737] smc91x: fix broken irq-context in PREEMPT_RT Date: Fri, 9 Jan 2026 12:40:56 +0100 Message-ID: <20260109112153.448403220@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260109112133.973195406@linuxfoundation.org> References: <20260109112133.973195406@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Yeoreum Yun [ Upstream commit 6402078bd9d1ed46e79465e1faaa42e3458f8a33 ] When smc91x.c is built with PREEMPT_RT, the following splat occurs in FVP_RevC: [ 13.055000] smc91x LNRO0003:00 eth0: link up, 10Mbps, half-duplex, lpa 0x0000 [ 13.062137] BUG: workqueue leaked atomic, lock or RCU: kworker/2:1[106] [ 13.062137] preempt=0x00000000 lock=0->0 RCU=0->1 workfn=mld_ifc_work [ 13.062266] C ** replaying previous printk message ** [ 13.062266] CPU: 2 UID: 0 PID: 106 Comm: kworker/2:1 Not tainted 6.18.0-dirty #179 PREEMPT_{RT,(full)} [ 13.062353] Hardware name: , BIOS [ 13.062382] Workqueue: mld mld_ifc_work [ 13.062469] Call trace: [ 13.062494] show_stack+0x24/0x40 (C) [ 13.062602] __dump_stack+0x28/0x48 [ 13.062710] dump_stack_lvl+0x7c/0xb0 [ 13.062818] dump_stack+0x18/0x34 [ 13.062926] process_scheduled_works+0x294/0x450 [ 13.063043] worker_thread+0x260/0x3d8 [ 13.063124] kthread+0x1c4/0x228 [ 13.063235] ret_from_fork+0x10/0x20 This happens because smc_special_trylock() disables IRQs even on PREEMPT_RT, but smc_special_unlock() does not restore IRQs on PREEMPT_RT. The reason is that smc_special_unlock() calls spin_unlock_irqrestore(), and rcu_read_unlock_bh() in __dev_queue_xmit() cannot invoke rcu_read_unlock() through __local_bh_enable_ip() when current->softirq_disable_cnt becomes zero. To address this issue, replace smc_special_trylock() with spin_trylock_irqsave(). Fixes: 342a93247e08 ("locking/spinlock: Provide RT variant header: ") Signed-off-by: Yeoreum Yun Reviewed-by: Simon Horman Link: https://patch.msgid.link/20251217085115.1730036-1-yeoreum.yun@arm.com Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin --- drivers/net/ethernet/smsc/smc91x.c | 10 +--------- 1 file changed, 1 insertion(+), 9 deletions(-) diff --git a/drivers/net/ethernet/smsc/smc91x.c b/drivers/net/ethernet/smsc/smc91x.c index 032eccf8eb42..7c2fdd02f1d3 100644 --- a/drivers/net/ethernet/smsc/smc91x.c +++ b/drivers/net/ethernet/smsc/smc91x.c @@ -515,15 +515,7 @@ static inline void smc_rcv(struct net_device *dev) * any other concurrent access and C would always interrupt B. But life * isn't that easy in a SMP world... */ -#define smc_special_trylock(lock, flags) \ -({ \ - int __ret; \ - local_irq_save(flags); \ - __ret = spin_trylock(lock); \ - if (!__ret) \ - local_irq_restore(flags); \ - __ret; \ -}) +#define smc_special_trylock(lock, flags) spin_trylock_irqsave(lock, flags) #define smc_special_lock(lock, flags) spin_lock_irqsave(lock, flags) #define smc_special_unlock(lock, flags) spin_unlock_irqrestore(lock, flags) #else -- 2.51.0