Re: [PATCH -v3 1/7] kexec jump: clean up #ifdef and comments

[Eric W. Biederman]

Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> writes:

> On Tue, 12 Aug 2008 11:14:21 +0800 Huang Ying <ying.huang@xxxxxxxxx> wrote:
>
>>  	xchg(&kexec_lock, 0);
>
> kernel/kexec.c: In function 'kernel_kexec':
> kernel/kexec.c:1501: warning: value computed is not used

A good question is why we are warned.

> Is there any reason why we cannot use the more conventional
> test_and_set_bit() etc, rather than this peculiarity?
>
> Or perhaps spin_trylock?

Totally odd.

Let me stop and take a look and see what has been changed.  The original
code used a xchg based read copy update scheme, which was extremely
compatible with a lot of goals.  The primary one being no blocking paths
in a successful kexec, and minimal dependence on library functions.

We need that minimal dependence to handle the kexec on panic case.

That doesn't rule out something like test_and_set_bit.

Eric
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