From: "Luck, Tony" <tony.luck@intel.com>
To: Liu hua <sdu.liu@huawei.com>, "anton@enomsg.org" <anton@enomsg.org>,
        "ccross@android.com" <ccross@android.com>,
        "keescook@chromium.org" <keescook@chromium.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
CC: Wang Nan <wangnan0@huawei.com>,
        "peifeiyue@huawei.com" <peifeiyue@huawei.com>
Subject: RE: Should Pstore(ramoops) records customized information?
Thread-Topic: Should Pstore(ramoops) records customized information?
Thread-Index: AQHPit0xXiBMDXiyt0+2L787Aem+Tpt3IwvA
Date: Wed, 18 Jun 2014 17:50:45 +0000
Message-ID: <3908561D78D1C84285E8C5FCA982C28F32838E10@ORSMSX114.amr.corp.intel.com>
References: <539E6D4D.5000802@huawei.com> <53A164DB.1020305@huawei.com>
In-Reply-To: <53A164DB.1020305@huawei.com>
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> (1) The backend (ramoops) provides servel memory regions staticly. Each region
>  is a ring buffer, which does not connect with certain PSTORE_TYPE_ID. So no one
>  can modify or use it before allocation.
>
> (2) A pstore user allocs a memory region, pstore will return a pstore_type_id.
>
>        pstore_type_id = alloc_pstroe_region()
>
> (3) This user record certain message to this region.
>
>        psinfo->write(pstore_type_id, ...)

Don't you need to match up the number of back-end ring buffer regions
with the number of users in the kernel that call alloc_pstore_region()?

Or do you envision that the backend can create these regions on demand?

Would different users need different sized regions? I think logging of
console messages might be able to work with a smaller ring buffer
than the ftrace logger. So perhaps we need a "size" argument when allocating?

Since these "regions" are in fact "ring buffers", the name of the allocation
routine should make that clear.  So call it "pstore_alloc_ring_buffer()"

After the system hangs/crashes ... how would you like pstore to
name these objects in /sys/fs/pstore/ for applications to pick them
up for analysis?  Maybe pstore_alloc_ring_buffer() needs a "char *name"
argument as well as a size?

-Tony
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