From: "Jürgen Groß" <jgross@suse.com>
To: Julien Grall <julien@xen.org>, xen-devel@lists.xenproject.org
Cc: Stefano Stabellini <sstabellini@kernel.org>, Wei Liu <wl@xen.org>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Ian Jackson <ian.jackson@eu.citrix.com>,
George Dunlap <george.dunlap@citrix.com>,
Jan Beulich <jbeulich@suse.com>
Subject: Re: [Xen-devel] [PATCH v3 5/6] xen/rcu: add assertions to debug build
Date: Fri, 6 Mar 2020 15:35:51 +0100 [thread overview]
Message-ID: <0e284f2e-0da6-9dc6-9b1e-d6966a8a36e8@suse.com> (raw)
In-Reply-To: <de613cc1-d444-7290-d96b-0d3193fce276@xen.org>
On 04.03.20 14:42, Julien Grall wrote:
> Hi,
>
> On 04/03/2020 06:32, Juergen Gross wrote:
>> diff --git a/xen/include/xen/rcupdate.h b/xen/include/xen/rcupdate.h
>> index 31c8b86d13..9f6d420898 100644
>> --- a/xen/include/xen/rcupdate.h
>> +++ b/xen/include/xen/rcupdate.h
>> @@ -34,10 +34,40 @@
>> #include <xen/cache.h>
>> #include <xen/spinlock.h>
>> #include <xen/cpumask.h>
>> -#include <xen/preempt.h>
>> +#include <xen/percpu.h>
>> +#include <asm/atomic.h>
>> #define __rcu
>> +#ifndef NDEBUG
>> +DECLARE_PER_CPU(unsigned int, rcu_lock_cnt);
>> +
>> +static inline void rcu_quiesce_disable(void)
>> +{
>> + this_cpu(rcu_lock_cnt)++;
>> + arch_lock_acquire_barrier();
>
> I am not sure to understand the goal of this barrier. What are you
> trying to protect against?
This is the result of a request by Roger, which seemed reasonable,
although I should have checked the suggested barrier type more
thoroughly.
He suggested to add barriers like in the former preempt_[en|dis]able()
cases, but to use the acquire and release barriers like in locks.
Thinking more about it I think a simple barrier() should do the trick as
only cpu local protection is needed.
Juergen
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next prev parent reply other threads:[~2020-03-06 14:36 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-04 6:32 [Xen-devel] [PATCH v3 0/6] xen/rcu: let rcu work better with core scheduling Juergen Gross
2020-03-04 6:32 ` [Xen-devel] [PATCH v3 1/6] xen/rcu: use rcu softirq for forcing quiescent state Juergen Gross
2020-03-04 6:32 ` [Xen-devel] [PATCH v3 2/6] xen/rcu: don't use stop_machine_run() for rcu_barrier() Juergen Gross
2020-03-04 6:32 ` [Xen-devel] [PATCH v3 3/6] xen: add process_pending_softirqs_norcu() for keyhandlers Juergen Gross
2020-03-04 6:32 ` [Xen-devel] [PATCH v3 4/6] xen/rcu: fix rcu_lock_domain() Juergen Gross
2020-03-04 6:32 ` [Xen-devel] [PATCH v3 5/6] xen/rcu: add assertions to debug build Juergen Gross
2020-03-04 13:42 ` Julien Grall
2020-03-06 14:35 ` Jürgen Groß [this message]
2020-03-06 16:08 ` Julien Grall
2020-03-04 6:32 ` [Xen-devel] [PATCH v3 6/6] xen/rcu: add per-lock counter in debug builds Juergen Gross
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