From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-vk0-f72.google.com (mail-vk0-f72.google.com [209.85.213.72]) by kanga.kvack.org (Postfix) with ESMTP id C35716B0388 for ; Tue, 21 Mar 2017 05:58:41 -0400 (EDT) Received: by mail-vk0-f72.google.com with SMTP id b202so44264616vka.7 for ; Tue, 21 Mar 2017 02:58:41 -0700 (PDT) Received: from mail-vk0-x22b.google.com (mail-vk0-x22b.google.com. [2607:f8b0:400c:c05::22b]) by mx.google.com with ESMTPS id o130si4237865vke.136.2017.03.21.02.58.40 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 21 Mar 2017 02:58:40 -0700 (PDT) Received: by mail-vk0-x22b.google.com with SMTP id x75so88773225vke.2 for ; Tue, 21 Mar 2017 02:58:40 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <005501d2a225$7ab66870$70233950$@alibaba-inc.com> References: <20170321091026.139655-1-dvyukov@google.com> <005501d2a225$7ab66870$70233950$@alibaba-inc.com> From: Dmitry Vyukov Date: Tue, 21 Mar 2017 10:58:19 +0100 Message-ID: Subject: Re: [PATCH] kcov: simplify interrupt check Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Hillf Danton Cc: Andrew Morton , "linux-mm@kvack.org" , Kefeng Wang , James Morse , Alexander Popov , Andrey Konovalov , LKML , syzkaller , Quentin Casasnovas On Tue, Mar 21, 2017 at 10:28 AM, Hillf Danton wrote: > > On March 21, 2017 5:10 PM Dmitry Vyukov wrote: >> >> @@ -60,15 +60,8 @@ void notrace __sanitizer_cov_trace_pc(void) >> /* >> * We are interested in code coverage as a function of a syscall inputs, >> * so we ignore code executed in interrupts. >> - * The checks for whether we are in an interrupt are open-coded, because >> - * 1. We can't use in_interrupt() here, since it also returns true >> - * when we are inside local_bh_disable() section. >> - * 2. We don't want to use (in_irq() | in_serving_softirq() | in_nmi()), >> - * since that leads to slower generated code (three separate tests, >> - * one for each of the flags). >> */ >> - if (!t || (preempt_count() & (HARDIRQ_MASK | SOFTIRQ_OFFSET >> - | NMI_MASK))) >> + if (!t || !in_task()) >> return; > > Nit: can we get the current task check cut off? Humm... good question. I don't remember why exactly I added it. I guess something was crashing during boot. Note that this call is inserted into almost all kernel code. But probably that was before I disabled instrumentation of some early boot code for other reasons (with KCOV_INSTRUMENT := n in Makefile), because now I can boot kernel in qemu without this check. But I am still not sure about real hardware/arm/etc. Does anybody know if current can ever (including early boot) return invalid pointer? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org