From: Oleg Nesterov <oleg@redhat.com>
To: Marco Elver <elver@google.com>
Cc: LKMM Maintainers -- Akira Yokosawa <akiyks@gmail.com>,
Alan Stern <stern@rowland.harvard.edu>,
Alexander Potapenko <glider@google.com>,
Andrea Parri <parri.andrea@gmail.com>,
Andrey Konovalov <andreyknvl@google.com>,
Andy Lutomirski <luto@kernel.org>,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
Arnd Bergmann <arnd@arndb.de>, Boqun Feng <boqun.feng@gmail.com>,
Borislav Petkov <bp@alien8.de>, Daniel Axtens <dja@axtens.net>,
Daniel Lustig <dlustig@nvidia.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
David Howells <dhowells@redhat.com>,
Dmitry Vyukov <dvyukov@google.com>,
"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
Jade Alglave <j.alglave@ucl.ac.uk>,
Joel Fernandes <joel@joelfernandes.org>,
Jonathan Corbet <corbet@lwn.net>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Luc Maranget <luc.maranget@inria.fr>,
Mark Rutland <mark.rutland@arm.com>,
Nicholas Piggin <npiggin@gmail.com>,
"Paul E. McKenney" <paulmck@linux.ibm.com>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Will Deacon <will@kernel.org>,
kasan-dev <kasan-dev@googlegroups.com>,
linux-arch <linux-arch@vger.kernel.org>,
"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
linux-efi@vger.kernel.org,
Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Linux Memory Management List <linux-mm@kvack.org>,
the arch/x86 maintainers <x86@kernel.org>
Subject: Re: [PATCH v2 1/8] kcsan: Add Kernel Concurrency Sanitizer infrastructure
Date: Wed, 23 Oct 2019 18:24:32 +0200 [thread overview]
Message-ID: <20191023162432.GC14327@redhat.com> (raw)
In-Reply-To: <CANpmjNPUT2B3rWaa=5Ee2Xs3HHDaUiBGpG09Q4h9Gemhsp9KFw@mail.gmail.com>
On 10/22, Marco Elver wrote:
>
> On Tue, 22 Oct 2019 at 17:49, Oleg Nesterov <oleg@redhat.com> wrote:
> >
> > Just for example. Suppose that task->state = TASK_UNINTERRUPTIBLE, this task
> > does __set_current_state(TASK_RUNNING), another CPU does wake_up_process(task)
> > which does the same UNINTERRUPTIBLE -> RUNNING transition.
> >
> > Looks like, this is the "data race" according to kcsan?
>
> Yes, they are "data races". They are probably not "race conditions" though.
>
> This is a fair distinction to make, and we never claimed to find "race
> conditions" only
I see, thanks, just wanted to be sure...
> KCSAN's goal is to find *data races* according to the LKMM. Some data
> races are race conditions (usually the more interesting bugs) -- but
> not *all* data races are race conditions. Those are what are usually
> referred to as "benign", but they can still become bugs on the wrong
> arch/compiler combination. Hence, the need to annotate these accesses
> with READ_ONCE, WRITE_ONCE or use atomic_t:
Well, if I see READ_ONCE() in the code I want to understand why it was
used. Is it really needed for correctness or we want to shut up kcsan?
Say, why should wait_event(wq, *ptr) use READ_ONCE()? Nevermind, please
forget.
Btw, why __kcsan_check_watchpoint() does user_access_save() before
try_consume_watchpoint() ?
Oleg.
next prev parent reply other threads:[~2019-10-23 16:24 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-17 14:12 [PATCH v2 0/8] Add Kernel Concurrency Sanitizer (KCSAN) Marco Elver
2019-10-17 14:12 ` [PATCH v2 1/8] kcsan: Add Kernel Concurrency Sanitizer infrastructure Marco Elver
2019-10-21 13:37 ` Alexander Potapenko
2019-10-21 15:54 ` Marco Elver
2019-10-22 14:11 ` Mark Rutland
2019-10-22 16:52 ` Marco Elver
2019-10-22 15:48 ` Oleg Nesterov
2019-10-22 17:42 ` Marco Elver
2019-10-23 16:24 ` Oleg Nesterov [this message]
2019-10-24 11:02 ` Marco Elver
2019-10-23 9:41 ` Dmitry Vyukov
2019-10-23 9:56 ` Dmitry Vyukov
2019-10-23 10:03 ` Dmitry Vyukov
2019-10-23 10:09 ` Dmitry Vyukov
2019-10-23 10:28 ` Dmitry Vyukov
2019-10-23 11:08 ` Dmitry Vyukov
2019-10-23 11:20 ` Dmitry Vyukov
2019-10-23 12:05 ` Dmitry Vyukov
2019-10-23 12:32 ` Dmitry Vyukov
2019-10-17 14:12 ` [PATCH v2 2/8] objtool, kcsan: Add KCSAN runtime functions to whitelist Marco Elver
2019-10-21 15:15 ` Dmitry Vyukov
2019-10-21 15:43 ` Marco Elver
2019-10-17 14:13 ` [PATCH v2 3/8] build, kcsan: Add KCSAN build exceptions Marco Elver
2019-10-17 14:13 ` [PATCH v2 4/8] seqlock, kcsan: Add annotations for KCSAN Marco Elver
2019-10-24 12:28 ` Mark Rutland
2019-10-24 14:17 ` Marco Elver
2019-10-24 16:35 ` Mark Rutland
2019-10-24 17:09 ` Marco Elver
2019-10-17 14:13 ` [PATCH v2 5/8] seqlock: Require WRITE_ONCE surrounding raw_seqcount_barrier Marco Elver
2019-10-17 14:13 ` [PATCH v2 6/8] asm-generic, kcsan: Add KCSAN instrumentation for bitops Marco Elver
2019-10-17 14:13 ` [PATCH v2 7/8] locking/atomics, kcsan: Add KCSAN instrumentation Marco Elver
2019-10-22 12:33 ` Mark Rutland
2019-10-22 18:17 ` Marco Elver
2019-10-17 14:13 ` [PATCH v2 8/8] x86, kcsan: Enable KCSAN for x86 Marco Elver
2019-10-22 12:59 ` Mark Rutland
2019-10-22 13:02 ` Marco Elver
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