From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id C3770C369D7 for ; Wed, 25 Sep 2024 12:18:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Type:In-Reply-To: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=QpX/TrTSTrn05ELx0yxQcZCW8GhD5VWBMkrKywZYZWM=; b=yPf3oedl+ITozyhnVuTki0AkP7 cuskfoW6TomYXfdllsjNxqjGcGGrQInAV3pzCDtpQDLuYexVjdWhR8yBOLU9GhnA63/vhk89H3dWc KzrnvkUrBih1hRKeaSsQxrF7lREUbkW5oqI5UrLf1yzRKNy6PgSngJTp4kIMHbYMxwrdcK6DWlvRd 45s5oJFrkUX4GHmHbTAY66iSLYkESgr/ju/ZK7r5jARDL/hJdjiQK2XYA6KxHKfWJLj4ko2evlPp6 RygjLguT6tQaZ4x7sJMI3TL9bkfM7Q8bnG4k447U9YNdgxSFtjm5tAtpjLQO6QOllK4bJswG38tXQ u8P8aLIw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1stQy2-000000055to-3Bah; Wed, 25 Sep 2024 12:18:02 +0000 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1stQmZ-0000000521e-0FGB for linux-arm-kernel@lists.infradead.org; Wed, 25 Sep 2024 12:06:13 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1727265968; 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: in-reply-to:in-reply-to:references:references; bh=QpX/TrTSTrn05ELx0yxQcZCW8GhD5VWBMkrKywZYZWM=; b=HEqhotj1PkUMXpqnipAH3Aa5nB84Boy9MJp3VKN4TqkHu2XuYDCerCrHkpKtet31NlFY4/ x1mnFhn7pBnVP/BV+XXIufj8PP2rAvgxELUozeXyoqSJjY/P55lZuZpNmS2KFJg7IykpTM GR5HkSbn/1ecYh6IJJwFXsOdTGHgMx8= Received: from mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-225-Y38F58PyMyi3vXMADCKbHg-1; Wed, 25 Sep 2024 08:06:07 -0400 X-MC-Unique: Y38F58PyMyi3vXMADCKbHg-1 Received: from mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (unknown [10.30.177.15]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 84256193E8E8; Wed, 25 Sep 2024 12:06:04 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.45.225.67]) by mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with SMTP id 24556195608A; Wed, 25 Sep 2024 12:06:00 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Wed, 25 Sep 2024 14:05:51 +0200 (CEST) Date: Wed, 25 Sep 2024 14:05:47 +0200 From: Oleg Nesterov To: chenqiwu Cc: corbet@lwn.net, catalin.marinas@arm.com, will@kernel.org, paulmck@kernel.org, akpm@linux-foundation.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org Subject: Re: [PATCH v4 2/2] arm64: show signal info for global init Message-ID: <20240925120546.GA26882@redhat.com> References: <20240924074341.37272-1-qiwu.chen@transsion.com> <20240924074341.37272-2-qiwu.chen@transsion.com> <20240924183634.GB17395@redhat.com> <20240925035440.GA2941@rlk> MIME-Version: 1.0 In-Reply-To: <20240925035440.GA2941@rlk> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240925_050611_210480_BB322368 X-CRM114-Status: GOOD ( 22.03 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 09/25, chenqiwu wrote: > > On Tue, Sep 24, 2024 at 08:36:35PM +0200, Oleg Nesterov wrote: > > > > So what does this patch try to do? Note that unhandled_signal(tsk) returns true > > if is_global_init(tsk). > > > > So it seems that this patch just tries to bypass the show_unhandled_signals and > > __ratelimit() checks? Or what? > > > Yes, this patch just try to bypass the show_unhandled_signals and > __ratelimit() checks for the global init. I think the changelog should explain this. But this doesn't look right to me, see below. > > OTOH. The is_global_init() check in unhandled_signal() (which predates the git > > history) doesn't look right to me. If init has a handler for, say, SIGSEGV, why > > should the kernel complain? I need to recheck this logic... > > > I think the orignal logic is the signal sent to the global init is > regarded as unhandled becuase it has SIGNAL_UNKILLABLE feature. And? How does this relate to SIGNAL_UNKILLABLE? Again, this check predates the git history and the SIGNAL_UNKILLABLE feature. And SIGNAL_UNKILLABLE has no effect in this case, see force_sig_info_to_task(). I am running this program void sigh(int sig) { printf("SIGSEGV %d\n", getpid()); execl("/usr/bin/sh", "sh", NULL); printf("exec failed\n"); } int main(void) { signal(SIGSEGV, sigh); *((char*)(1234)) = 0; return 1; } as a global init under KVM. It works but dmesg reports init[1]: segfault at 4d2 ip 00000000004006b5 sp 00007ffcf2975170 error 6 in init[6b5,400000+1000] likely on CPU 0 (core 0, socket 0) Code: e8 c0 fe ff ff bf 6b 07 40 00 e8 56 fe ff ff 90 c9 c3 55 48 89 e5 be 56 06 40 00 bf 0b 00 00 00 e8 80 fe ff ff b8 d2 04 00 00 00 00 b8 01 00 00 00 5d c3 90 41 57 41 56 41 89 ff 41 55 41 54 I'll send the patch which removes the is_global_init check from unhandled_signal() which actually has more problems, afaics. But this all is offtopic. Oleg.