From: Ingo Molnar <mingo@kernel.org>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: "Andy Lutomirski" <luto@kernel.org>,
x86@kernel.org, linux-kernel@vger.kernel.org,
"Frédéric Weisbecker" <fweisbec@gmail.com>,
"Rik van Riel" <riel@redhat.com>,
"Oleg Nesterov" <oleg@redhat.com>,
"Denys Vlasenko" <vda.linux@googlemail.com>,
"Borislav Petkov" <bp@alien8.de>,
"Kees Cook" <keescook@chromium.org>,
"Brian Gerst" <brgerst@gmail.com>
Subject: Re: [RFC/INCOMPLETE 01/13] context_tracking: Add context_tracking_assert_state
Date: Tue, 30 Jun 2015 13:04:14 +0200 [thread overview]
Message-ID: <20150630110414.GA25988@gmail.com> (raw)
In-Reply-To: <20150618225420.GQ3913@linux.vnet.ibm.com>
* Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote:
> > Yeah, and inverting the condition. Assuming the condition was assert()-style
> > inverted to begin with! :-)
>
> It appears to have been. ;-)
>
> Please see below for an untested patch. I made this be one big patch, but could
> have one patch add RCU_LOCKDEP_WARN(), a series convert uses from
> rcu_lockdep_assert() to RCU_LOCKDEP_WARN(), and a final patch remove
> rcu_lockdep_assert(). Let me know!
One big patch is perfect I think - it's a rename and a relatively mechanic
inversion of conditions, no point in splitting it up any more IMHO. (But it's your
call really.)
So I had a quick look at this patch, and IMHO the RCU_LOCKDEP_WARN() lines read a
lot more 'naturally', because the new, inverted conditions now highlight buggy
scenarios - which has the same logic parity as the kernel's historic
WARN_ON()/BUG_ON() patterns:
Reviewed-by: Ingo Molnar <mingo@kernel.org>
This one looked a bit weird:
> index a0a0dd03c73a..47268fb1d27b 100644
> --- a/kernel/rcu/update.c
> +++ b/kernel/rcu/update.c
> @@ -589,8 +589,8 @@ EXPORT_SYMBOL_GPL(call_rcu_tasks);
> void synchronize_rcu_tasks(void)
> {
> /* Complain if the scheduler has not started. */
> - rcu_lockdep_assert(!rcu_scheduler_active,
> - "synchronize_rcu_tasks called too soon");
> + RCU_LOCKDEP_WARN(rcu_scheduler_active,
> + "synchronize_rcu_tasks called too soon");
>
So I'd assume that a flag called 'rcu_scheduler_active' would be 1 if the RCU
scheduler is active.
So why do we warn on it being active? Shouldn't the condition be:
RCU_LOCKDEP_WARN(!rcu_scheduler_active,
"synchronize_rcu_tasks called too soon");
I.e. we warn when the RCU scheduler is not yet active and we called
synchronize_rcu_tasks() too soon?
So either the original assert() was wrong, or I'm missing something obvious?
Thanks,
Ingo
next prev parent reply other threads:[~2015-06-30 11:04 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-16 20:16 [RFC/INCOMPLETE 00/13] x86: Rewrite exit-to-userspace code Andy Lutomirski
2015-06-16 20:16 ` [RFC/INCOMPLETE 01/13] context_tracking: Add context_tracking_assert_state Andy Lutomirski
2015-06-17 9:41 ` Ingo Molnar
2015-06-17 14:15 ` Andy Lutomirski
2015-06-18 9:57 ` Ingo Molnar
2015-06-18 11:07 ` Andy Lutomirski
2015-06-18 15:52 ` Andy Lutomirski
2015-06-18 16:17 ` Ingo Molnar
2015-06-18 16:26 ` Frederic Weisbecker
2015-06-18 19:26 ` Andy Lutomirski
2015-06-17 15:27 ` Paul E. McKenney
2015-06-18 9:59 ` Ingo Molnar
2015-06-18 22:54 ` Paul E. McKenney
2015-06-19 2:19 ` Paul E. McKenney
2015-06-30 11:04 ` Ingo Molnar [this message]
2015-06-30 16:16 ` Paul E. McKenney
2015-06-16 20:16 ` [RFC/INCOMPLETE 02/13] notifiers: Assert that RCU is watching in notify_die Andy Lutomirski
2015-06-16 20:16 ` [RFC/INCOMPLETE 03/13] x86: Move C entry and exit code to arch/x86/entry/common.c Andy Lutomirski
2015-06-16 20:16 ` [RFC/INCOMPLETE 04/13] x86/traps: Assert that we're in CONTEXT_KERNEL in exception entries Andy Lutomirski
2015-06-16 20:16 ` [RFC/INCOMPLETE 05/13] x86/entry: Add enter_from_user_mode and use it in syscalls Andy Lutomirski
2015-06-16 20:16 ` [RFC/INCOMPLETE 06/13] x86/entry: Add new, comprehensible entry and exit hooks Andy Lutomirski
2015-06-16 20:16 ` [RFC/INCOMPLETE 07/13] x86/entry/64: Really create an error-entry-from-usermode code path Andy Lutomirski
2015-06-16 20:16 ` [RFC/INCOMPLETE 08/13] x86/entry/64: Migrate 64-bit syscalls to new exit hooks Andy Lutomirski
2015-06-17 10:00 ` Ingo Molnar
2015-06-17 10:02 ` Ingo Molnar
2015-06-17 14:12 ` Andy Lutomirski
2015-06-18 10:17 ` Ingo Molnar
2015-06-18 10:19 ` Ingo Molnar
2015-06-16 20:16 ` [RFC/INCOMPLETE 09/13] x86/entry/compat: Migrate compat " Andy Lutomirski
2015-06-16 20:16 ` [RFC/INCOMPLETE 10/13] x86/asm/entry/64: Save all regs on interrupt entry Andy Lutomirski
2015-06-16 20:16 ` [RFC/INCOMPLETE 11/13] x86/asm/entry/64: Simplify irq stack pt_regs handling Andy Lutomirski
2015-06-16 20:16 ` [RFC/INCOMPLETE 12/13] x86/asm/entry/64: Migrate error and interrupt exit work to C Andy Lutomirski
2015-06-16 20:16 ` [RFC/INCOMPLETE 13/13] x86/entry: Remove SCHEDULE_USER and asm/context-tracking.h Andy Lutomirski
2015-06-17 9:48 ` [RFC/INCOMPLETE 00/13] x86: Rewrite exit-to-userspace code Ingo Molnar
2015-06-17 10:13 ` Richard Weinberger
2015-06-17 11:04 ` Ingo Molnar
2015-06-17 14:19 ` Andy Lutomirski
2015-06-17 15:16 ` Andy Lutomirski
2015-06-18 10:14 ` Ingo Molnar
2015-06-17 10:32 ` Ingo Molnar
2015-06-17 11:14 ` Ingo Molnar
2015-06-17 14:23 ` Andy Lutomirski
2015-06-18 10:11 ` Ingo Molnar
2015-06-18 11:06 ` Andy Lutomirski
2015-06-18 16:24 ` Ingo Molnar
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