From: Gao Xiang <gaoxiang25@huawei.com>
To: Andrea Parri <andrea.parri@amarulasolutions.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
<devel@driverdev.osuosl.org>, <linux-erofs@lists.ozlabs.org>,
Chao Yu <yuchao0@huawei.com>, LKML <linux-kernel@vger.kernel.org>,
<weidu.du@huawei.com>, Miao Xie <miaoxie@huawei.com>
Subject: Re: [PATCH 05/10] staging: erofs: add a full barrier in erofs_workgroup_unfreeze
Date: Fri, 23 Nov 2018 18:00:25 +0800 [thread overview]
Message-ID: <5bf95ae0-cecb-c220-653b-704baee1cd8e@huawei.com> (raw)
In-Reply-To: <20181123094739.GA3487@andrea>
Hi Andrea,
On 2018/11/23 17:51, Andrea Parri wrote:
> Correct. This is informally documented in Documentation/atomic_t.txt
> and formalized within tools/memory-model/.
>
>
>> I don't know whether my understanding is correct, If I am wrong..please correct me, or
>> I need to add more detailed code comments to explain in the code?
> Yes, please; please review the above points (including 1. and 3.) and
> try to address them with inline comments. Maybe (if that matches the
> *behavior*/guarantee you have in mind...) something like:
>
> [in erofs_workgroup_unfreeze()]
>
> /*
> * Orders the store/load to/from [???] and the store to
> * ->refcount performed by the atomic_set() below.
> *
> * Matches the atomic_cmpxchg() in erofs_workgroup_get().
> *
> * Guarantees that if a successful atomic_cmpxchg() reads
> * the value stored by the atomic_set() then [???].
> */
> smp_mb();
> atomic_set(&grp->refcount, v);
>
>
> [in erofs_workgroup_get()]
>
> /*
> * Orders the load from ->refcount performed by the
> * atomic_cmpxchg() below and the store/load [???].
> *
> * See the comment for the smp_mb() in
> * erofs_workgroup_unfreeze().
> */
> if (unlikely(atomic_cmpxchg(&grp->refcount, o, o + 1) != o))
> goto repeat;
>
OK, I will add these comments in the next version patchset, will be sent later.
Thanks for your suggestion. :)
Thanks,
Gao Xiang
> Thanks,
> Andrea
>
>
next prev parent reply other threads:[~2018-11-23 10:00 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-20 14:34 [PATCH 00/10] staging: erofs: decompression stability enhancement Gao Xiang
2018-11-20 14:34 ` [PATCH 01/10] staging: erofs: fix `trace_erofs_readpage' position Gao Xiang
2018-11-22 10:19 ` Greg Kroah-Hartman
2018-11-22 10:49 ` Gao Xiang
2018-11-22 11:00 ` Greg Kroah-Hartman
2018-11-20 14:34 ` [PATCH 02/10] staging: erofs: fix race when the managed cache is enabled Gao Xiang
2018-11-22 10:17 ` Greg Kroah-Hartman
2018-11-22 10:42 ` Gao Xiang
2018-11-22 11:06 ` Greg Kroah-Hartman
2018-11-22 11:43 ` Gao Xiang
2018-11-22 12:26 ` Greg Kroah-Hartman
2018-11-22 12:41 ` Gao Xiang
2018-11-22 13:20 ` Greg Kroah-Hartman
2018-11-22 10:19 ` Greg Kroah-Hartman
2018-11-20 14:34 ` [PATCH 03/10] staging: erofs: atomic_cond_read_relaxed on ref-locked workgroup Gao Xiang
2018-11-22 10:20 ` Greg Kroah-Hartman
2018-11-20 14:34 ` [PATCH 04/10] staging: erofs: fix `erofs_workgroup_{try_to_freeze, unfreeze}' Gao Xiang
2018-11-22 10:21 ` Greg Kroah-Hartman
2018-11-22 10:29 ` Gao Xiang
2018-11-22 11:03 ` Greg Kroah-Hartman
2018-11-22 11:05 ` Greg Kroah-Hartman
2018-11-22 11:22 ` Gao Xiang
2018-11-20 14:34 ` [PATCH 05/10] staging: erofs: add a full barrier in erofs_workgroup_unfreeze Gao Xiang
2018-11-22 10:22 ` Greg Kroah-Hartman
2018-11-22 10:56 ` Gao Xiang
2018-11-22 18:50 ` Andrea Parri
2018-11-23 2:51 ` Gao Xiang
2018-11-23 9:51 ` Andrea Parri
2018-11-23 10:00 ` Gao Xiang [this message]
2018-11-20 14:34 ` [PATCH 06/10] staging: erofs: fix the definition of DBG_BUGON Gao Xiang
2018-11-20 14:34 ` [PATCH 07/10] staging: erofs: separate into init_once / always Gao Xiang
2018-11-22 10:23 ` Greg Kroah-Hartman
2018-11-22 10:34 ` Gao Xiang
2018-11-22 11:05 ` Greg Kroah-Hartman
2018-11-22 11:11 ` Gao Xiang
2018-11-22 11:26 ` Greg Kroah-Hartman
2018-11-22 11:37 ` Gao Xiang
2018-11-22 12:00 ` Gao Xiang
2018-11-22 13:01 ` Gao Xiang
2018-11-22 13:23 ` Greg Kroah-Hartman
2018-11-22 13:59 ` Gao Xiang
2018-11-20 14:34 ` [PATCH 08/10] staging: erofs: locked before registering for all new workgroups Gao Xiang
2018-11-22 10:24 ` Greg Kroah-Hartman
2018-11-22 10:35 ` Gao Xiang
2018-11-20 14:34 ` [PATCH 09/10] staging: erofs: decompress asynchronously if PG_readahead page at first Gao Xiang
2018-11-20 14:34 ` [PATCH 10/10] staging: erofs: rename strange variable names in z_erofs_vle_frontend Gao Xiang
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