From: "Paul E. McKenney" <paulmck@kernel.org>
To: Marco Elver <elver@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>,
"Uladzislau Rezki (Sony)" <urezki@gmail.com>,
RCU <rcu@vger.kernel.org>,
Neeraj upadhyay <Neeraj.Upadhyay@amd.com>,
Boqun Feng <boqun.feng@gmail.com>,
Hillf Danton <hdanton@sina.com>,
Joel Fernandes <joel@joelfernandes.org>,
LKML <linux-kernel@vger.kernel.org>,
Oleksiy Avramchenko <oleksiy.avramchenko@sony.com>,
Frederic Weisbecker <frederic@kernel.org>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH 25/48] rcu: Mark writes to rcu_sync ->gp_count field
Date: Tue, 14 May 2024 09:54:39 -0700 [thread overview]
Message-ID: <4ffb46f8-9b45-472b-93a8-18d0a3bba8d6@paulmck-laptop> (raw)
In-Reply-To: <CANpmjNMUJ6UMwWAEHfm-7WZ=jKD56PH67Zp8dB6B=fEysiK=Hw@mail.gmail.com>
On Mon, May 13, 2024 at 04:13:35PM +0200, Marco Elver wrote:
> On Fri, 10 May 2024 at 16:11, Paul E. McKenney <paulmck@kernel.org> wrote:
> [...]
> > > > Does this mean that KCSAN/etc treats the files in kernel/rcu/
> > > > differently than the "Rest of Kernel"? Or what?
> > > >
> > > > And how is it enforced?
> > >
> > > I can only find the strnstr(buf, "rcu") checks in skip_report(),
> > > but they only cover the KCSAN_REPORT_VALUE_CHANGE_ONLY case...
> >
> > Huh, new one on me! When I run KCSAN, I set CONFIG_KCSAN_STRICT=y,
> > which implies CONFIG_KCSAN_REPORT_VALUE_CHANGE_ONLY=n, which should
> > prevent skip_report() from even being invoked.
>
> The strnstr hack goes back to the first version of KCSAN released in
> v5.8 [1]. It was added in response to Paul wanting the "stricter"
> treatment for RCU even while KCSAN was still in development, and back
> then syzbot was the first test system using KCSAN. Shortly after Paul
> added a KCSAN config for rcutorture with a laundry list of options to
> make KCSAN "strict" (before we eventually added CONFIG_KCSAN_STRICT
> which greatly simplified that).
>
> While the strnstr(.., "rcu") rules are redundant when using the
> stricter rules (at least CONFIG_KCSAN_REPORT_VALUE_CHANGE_ONLY=n is
> set), we're keeping the "rcu" special case around because there are
> test robots and fuzzers that use the default KCSAN config (unlike
> rcutorture). And because we know that RCU likes the stricter rules,
> the "value change only" filter is ignored in all KCSAN configs for
> rcu-related functions.
>
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/kernel/kcsan/report.c?id=v5.8
Thank you for the background information!
> Back then syzbot occasionally reported RCU data races, but these days
> rcutorture probably finds all of them before syzbot ever gets its
> hands on new code.
I do try my best. ;-)
Thanx, Paul
next prev parent reply other threads:[~2024-05-14 16:54 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-07 9:34 [PATCH 00/48] RCU changes for v6.10 Uladzislau Rezki (Sony)
2024-05-07 9:34 ` [PATCH 01/48] scftorture: Increase memory provided to guest OS Uladzislau Rezki (Sony)
2024-05-07 9:34 ` [PATCH 02/48] rcutorture: Disable tracing to permit Tasks Rude RCU testing Uladzislau Rezki (Sony)
2024-05-07 9:34 ` [PATCH 03/48] rcu: Add lockdep checks and kernel-doc header to rcu_softirq_qs() Uladzislau Rezki (Sony)
2024-05-07 9:34 ` [PATCH 04/48] rcutorture: Enable RCU priority boosting for TREE09 Uladzislau Rezki (Sony)
2024-05-07 9:34 ` [PATCH 05/48] rcutorture: Dump # online CPUs on insufficient cb-flood laundering Uladzislau Rezki (Sony)
2024-05-07 9:34 ` [PATCH 06/48] rcutorture: Dump GP kthread state " Uladzislau Rezki (Sony)
2024-05-07 9:34 ` [PATCH 07/48] rcutorture: ASSERT_EXCLUSIVE_WRITER() for ->rtort_pipe_count updates Uladzislau Rezki (Sony)
2024-05-07 9:34 ` [PATCH 08/48] rcu-tasks: Make Tasks RCU wait idly for grace-period delays Uladzislau Rezki (Sony)
2024-05-07 9:34 ` [PATCH 09/48] doc: Remove references to arrayRCU.rst Uladzislau Rezki (Sony)
2024-05-07 9:34 ` [PATCH 10/48] MAINTAINERS: Update Neeraj's email address Uladzislau Rezki (Sony)
2024-05-07 9:34 ` [PATCH 11/48] bpf: Select new NEED_TASKS_RCU Kconfig option Uladzislau Rezki (Sony)
2024-05-07 9:34 ` [PATCH 12/48] arch: " Uladzislau Rezki (Sony)
2024-05-07 9:34 ` [PATCH 13/48] rcu: Add data structures for synchronize_rcu() Uladzislau Rezki (Sony)
2024-05-07 9:34 ` [PATCH 14/48] tracing: Select new NEED_TASKS_RCU Kconfig option Uladzislau Rezki (Sony)
2024-05-07 9:34 ` [PATCH 15/48] bpf: Choose RCU Tasks based on TASKS_RCU rather than PREEMPTION Uladzislau Rezki (Sony)
2024-05-07 9:34 ` [PATCH 16/48] ftrace: " Uladzislau Rezki (Sony)
2024-05-07 9:34 ` [PATCH 17/48] rcu: Update lockdep while in RCU read-side critical section Uladzislau Rezki (Sony)
2024-05-07 9:35 ` [PATCH 18/48] rcu: Make TINY_RCU depend on !PREEMPT_RCU rather than !PREEMPTION Uladzislau Rezki (Sony)
2024-05-07 9:35 ` [PATCH 19/48] srcu: Make Tiny SRCU explicitly disable preemption Uladzislau Rezki (Sony)
2024-05-07 9:35 ` [PATCH 20/48] rcu: Create NEED_TASKS_RCU to factor out enablement logic Uladzislau Rezki (Sony)
2024-05-07 9:35 ` [PATCH 21/48] rcu: Remove redundant BH disabling in TINY_RCU Uladzislau Rezki (Sony)
2024-05-07 9:35 ` [PATCH 22/48] rcu: Make Tiny RCU explicitly disable preemption Uladzislau Rezki (Sony)
2024-05-07 9:35 ` [PATCH 23/48] rcu: Remove redundant READ_ONCE() of rcu_state.gp_flags in tree.c Uladzislau Rezki (Sony)
2024-05-07 9:35 ` [PATCH 24/48] rcu: Bring diagnostic read of rcu_state.gp_flags into alignment Uladzislau Rezki (Sony)
2024-05-07 9:35 ` [PATCH 25/48] rcu: Mark writes to rcu_sync ->gp_count field Uladzislau Rezki (Sony)
2024-05-07 14:54 ` Oleg Nesterov
2024-05-07 17:44 ` Paul E. McKenney
2024-05-09 15:13 ` Oleg Nesterov
2024-05-10 3:59 ` Paul E. McKenney
2024-05-10 11:31 ` Oleg Nesterov
2024-05-10 14:00 ` Alan Huang
2024-05-10 14:04 ` Paul E. McKenney
2024-05-12 10:53 ` Oleg Nesterov
2024-05-12 14:57 ` Paul E. McKenney
2024-05-10 13:18 ` Oleg Nesterov
2024-05-10 13:50 ` Oleg Nesterov
2024-05-10 14:11 ` Paul E. McKenney
2024-05-12 10:41 ` Oleg Nesterov
2024-05-13 14:13 ` Marco Elver
2024-05-14 16:54 ` Paul E. McKenney [this message]
2024-05-10 13:58 ` Paul E. McKenney
2024-05-12 11:19 ` [PATCH] rcu/sync: don't read rcu_sync->gp_count lockless Oleg Nesterov
2024-05-12 15:10 ` Paul E. McKenney
2024-05-12 16:55 ` Oleg Nesterov
2024-05-12 17:11 ` Paul E. McKenney
2024-05-12 18:06 ` Oleg Nesterov
2024-05-07 9:35 ` [PATCH 26/48] rcu: Mark loads from rcu_state.n_online_cpus Uladzislau Rezki (Sony)
2024-05-07 9:35 ` [PATCH 27/48] rcu: Make hotplug operations track GP state, not flags Uladzislau Rezki (Sony)
2024-05-07 9:35 ` [PATCH 28/48] rcu: Inform KCSAN of one-byte cmpxchg() in rcu_trc_cmpxchg_need_qs() Uladzislau Rezki (Sony)
2024-05-07 9:35 ` [PATCH 29/48] rcu: Remove redundant CONFIG_PROVE_RCU #if condition Uladzislau Rezki (Sony)
2024-05-07 9:35 ` [PATCH 30/48] rcu-tasks: Replace exit_tasks_rcu_start() initialization with WARN_ON_ONCE() Uladzislau Rezki (Sony)
2024-05-07 9:35 ` [PATCH 31/48] rcu-tasks: Fix the comments for tasks_rcu_exit_srcu_stall_timer Uladzislau Rezki (Sony)
2024-05-07 9:35 ` [PATCH 32/48] rcu-tasks: Fix show_rcu_tasks_trace_gp_kthread buffer overflow Uladzislau Rezki (Sony)
2024-05-07 9:35 ` [PATCH 33/48] rcu: Mollify sparse with RCU guard Uladzislau Rezki (Sony)
2024-05-07 9:35 ` [PATCH 34/48] rcu: Fix buffer overflow in print_cpu_stall_info() Uladzislau Rezki (Sony)
2024-05-07 9:35 ` [PATCH 35/48] rcu: Reduce synchronize_rcu() latency Uladzislau Rezki (Sony)
2024-05-07 9:35 ` [PATCH 36/48] rcu: Add a trace event for synchronize_rcu_normal() Uladzislau Rezki (Sony)
2024-05-07 9:35 ` [PATCH 37/48] rcu: Support direct wake-up of synchronize_rcu() users Uladzislau Rezki (Sony)
2024-05-07 9:35 ` [PATCH 38/48] rcu: Allocate WQ with WQ_MEM_RECLAIM bit set Uladzislau Rezki (Sony)
2024-05-07 9:35 ` [PATCH 39/48] rcutorture: Remove extraneous rcu_torture_pipe_update_one() READ_ONCE() Uladzislau Rezki (Sony)
2024-05-07 9:35 ` [PATCH 40/48] rcutorture: Fix rcu_torture_one_read() pipe_count overflow comment Uladzislau Rezki (Sony)
2024-05-07 9:35 ` [PATCH 41/48] rcutorture: Re-use value stored to ->rtort_pipe_count instead of re-reading Uladzislau Rezki (Sony)
2024-05-07 9:35 ` [PATCH 42/48] rcutorture: Use the gp_kthread_dbg operation specified by cur_ops Uladzislau Rezki (Sony)
2024-05-07 9:35 ` [PATCH 43/48] rcutorture: Make rcutorture support print rcu-tasks gp state Uladzislau Rezki (Sony)
2024-05-07 9:35 ` [PATCH 44/48] rcutorture: Removing redundant function pointer initialization Uladzislau Rezki (Sony)
2024-05-07 9:35 ` [PATCH 45/48] rcutorture: Make stall-tasks directly exit when rcutorture tests end Uladzislau Rezki (Sony)
2024-05-07 9:35 ` [PATCH 46/48] rcutorture: Fix invalid context warning when enable srcu barrier testing Uladzislau Rezki (Sony)
2024-05-07 9:35 ` [PATCH 47/48] torture: Scale --do-kvfree test time Uladzislau Rezki (Sony)
2024-05-07 9:35 ` [PATCH 48/48] rcutorture: Use rcu_gp_slow_register/unregister() only for rcutype test Uladzislau Rezki (Sony)
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