From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Mon, 29 Oct 2018 19:08:44 +0100 (CET) Received: from mail-pg1-x541.google.com ([IPv6:2607:f8b0:4864:20::541]:40673 "EHLO mail-pg1-x541.google.com" rhost-flags-OK-OK-OK-OK) by eddie.linux-mips.org with ESMTP id S23994240AbeJ2SIk3CqaY (ORCPT ); Mon, 29 Oct 2018 19:08:40 +0100 Received: by mail-pg1-x541.google.com with SMTP id o14-v6so4288936pgv.7 for ; Mon, 29 Oct 2018 11:08:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=5KlK5EoYecHiEwx2KYOj1AK3WWuK24K/BTuRZp/Hgn0=; b=ViKF3X5QZz1G04Kuc+UrpCLOIvvtASddvUpgEhbE2NwCsDxuq6JsW/AfF3MtdzfNcH x4aFvJIFkNdrS8l2CQjvpOEnAdP+LsFKZAoe9CdyAH5M9odaITFSuzPbsiwDohBeU3UQ YDDibS0wr7JOOkRxMW/g3gib7jVbkYmN9FZJo= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=5KlK5EoYecHiEwx2KYOj1AK3WWuK24K/BTuRZp/Hgn0=; b=Iw8f5EJv1yKrBQ9k4lPek0vfM/fdoWfo9bKbwwDU8DE5GYhzAQeH+WJuy4OGva/szB RUbL9C8+6VNxQq9Ue1Q0qVnD7OZSEFn8Arh4t1Kx+JsHc9ybgCJPL5xKIksTgQpgnKgv tsJiD+3Zmj/twrzyBEHFd8wWyTWWcM5xfGBOG0ydcLteUNEvA7XR9TUmK4Qqks6Y5LFN bjv/yORP58BNrshFx6eVyKVqTQChY7IeG43u207EW0x/ri92lAMPvcjqFdvlQytkMHGn NzpczMX6Lk1aUgmoxl2n03IoJwJZHVQHFBaRZgm4i0Ca+QzSxJY2OdMIFWbIWnIPKtQ/ r4EQ== X-Gm-Message-State: AGRZ1gJYhxCItRxYiY2Kd1mCkSRSFqgZhzODWkyNTCD2d/lxF/KCF9JW uJ8cHiMDnuaGT7HmWzTZ7iJYJQ== X-Google-Smtp-Source: AJdET5dnes+lqSdsKf+M8kej513uIWGXuNg0nbxyLNaYWMhztTpOmHr2lEByvMdxDcC5rsUHz1VWbw== X-Received: by 2002:a62:7a92:: with SMTP id v140-v6mr9434788pfc.46.1540836514355; Mon, 29 Oct 2018 11:08:34 -0700 (PDT) Received: from tictac2.mtv.corp.google.com ([2620:15c:202:1:c8e0:70d7:4be7:a36]) by smtp.gmail.com with ESMTPSA id u13-v6sm20537765pgp.18.2018.10.29.11.08.32 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 29 Oct 2018 11:08:33 -0700 (PDT) From: Douglas Anderson To: Jason Wessel , Daniel Thompson , tglx@linutronix.de, mingo@kernel.org, gregkh@linuxfoundation.org Cc: linux-arm-msm@vger.kernel.org, kgdb-bugreport@lists.sourceforge.net, Douglas Anderson , linux-mips@linux-mips.org, linux-sh@vger.kernel.org, peterz@infradead.org, linux-hexagon@vger.kernel.org, frederic@kernel.org, riel@surriel.com, linux-kernel@vger.kernel.org, luto@kernel.org, sparclinux@vger.kernel.org, linux-snps-arc@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH 6/7] smp: Don't yell about IRQs disabled in kgdb_roundup_cpus() Date: Mon, 29 Oct 2018 11:07:06 -0700 Message-Id: <20181029180707.207546-7-dianders@chromium.org> X-Mailer: git-send-email 2.19.1.568.g152ad8e336-goog In-Reply-To: <20181029180707.207546-1-dianders@chromium.org> References: <20181029180707.207546-1-dianders@chromium.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 66977 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: dianders@chromium.org Precedence: bulk List-help: List-unsubscribe: List-software: Ecartis version 1.0.0 List-Id: linux-mips X-List-ID: linux-mips List-subscribe: List-owner: List-post: List-archive: X-list: linux-mips In kgdb_roundup_cpus() we've got code that looks like: local_irq_enable(); smp_call_function(kgdb_call_nmi_hook, NULL, 0); local_irq_disable(); In certain cases when we drop into kgdb (like with sysrq-g on a serial console) we'll get a big yell that looks like: sysrq: SysRq : DEBUG ------------[ cut here ]------------ DEBUG_LOCKS_WARN_ON(current->hardirq_context) WARNING: CPU: 0 PID: 0 at .../kernel/locking/lockdep.c:2875 lockdep_hardirqs_on+0xf0/0x160 CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.19.0 #27 pstate: 604003c9 (nZCv DAIF +PAN -UAO) pc : lockdep_hardirqs_on+0xf0/0x160 ... Call trace: lockdep_hardirqs_on+0xf0/0x160 trace_hardirqs_on+0x188/0x1ac kgdb_roundup_cpus+0x14/0x3c kgdb_cpu_enter+0x53c/0x5cc kgdb_handle_exception+0x180/0x1d4 kgdb_compiled_brk_fn+0x30/0x3c brk_handler+0x134/0x178 do_debug_exception+0xfc/0x178 el1_dbg+0x18/0x78 kgdb_breakpoint+0x34/0x58 sysrq_handle_dbg+0x54/0x5c __handle_sysrq+0x114/0x21c handle_sysrq+0x30/0x3c qcom_geni_serial_isr+0x2dc/0x30c ... ... irq event stamp: ...45 hardirqs last enabled at (...44): [...] __do_softirq+0xd8/0x4e4 hardirqs last disabled at (...45): [...] el1_irq+0x74/0x130 softirqs last enabled at (...42): [...] _local_bh_enable+0x2c/0x34 softirqs last disabled at (...43): [...] irq_exit+0xa8/0x100 ---[ end trace adf21f830c46e638 ]--- Let's add kgdb to the list of reasons not to warn in smp_call_function_many(). That will allow us (in a future patch) to stop calling local_irq_enable() which will get rid of the original splat. NOTE: with this change comes the obvious question: will we start deadlocking more often now when we drop into the debugger. I can't say that for sure one way or the other, but the fact that we do the same logic for "oops_in_progress" makes me feel like it shouldn't happen too often. Also note that the old logic of turning on interrupts temporarily wasn't exactly safe since (I presume) that could have violated spin_lock_irqsave() semantics and ended up with a deadlock of its own. Signed-off-by: Douglas Anderson --- kernel/smp.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/smp.c b/kernel/smp.c index 163c451af42e..bb581e58c8dc 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -19,6 +19,7 @@ #include #include #include +#include #include "smpboot.h" @@ -413,7 +414,8 @@ void smp_call_function_many(const struct cpumask *mask, * can't happen. */ WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled() - && !oops_in_progress && !early_boot_irqs_disabled); + && !oops_in_progress && !early_boot_irqs_disabled + && !in_dbg_master()); /* Try to fastpath. So, what's a CPU they want? Ignoring this one. */ cpu = cpumask_first_and(mask, cpu_online_mask); -- 2.19.1.568.g152ad8e336-goog