Re: [PATCH] Syscalls: reboot: Add options to the reboot syscall toremount filesystems ro

[Scott James Remnant]

On Thu, Mar 3, 2011 at 6:48 PM, Mark Lord <kernel@xxxxxxxxxxxx> wrote:
> On 11-03-03 09:33 PM, Linus Torvalds wrote:
>> On Thu, Mar 3, 2011 at 6:00 PM, Ken Sumrall <ksumrall@xxxxxxxxxxx> wrote:
>>>
>>> Writing a single byte to /proc/sysrq-trigger is an asynchronous
>>> operation, with no obvious way to be informed that it has completed
>>> the remount.
>>
>> Right you are. That's something of a misfeature, but it comes from the
>> way sysrq works: obviously the "real" sysrq thing is about keyboard
>> input, so all the sysrq stuff has to be async.
>>
>> The fact that that async nature then ends up also affecting the
>> /proc/sysrq-trigger case (which _could_ be synchronous) is a bit sad
>> in this case.
>
> Agreed.
>
> I have the echo s/u to sysrq-trigger (plus a 2-sec sleep ala MS-Win)
> on my Ubuntu systems here, because their shutdown "sequence"
> is racy and buggy, and frequently powers off the box with the
> rootfs still mounted rw otherwise.
>
> And don't get me started about the races on system startup
>  -- "upstart" is an abomination, or at least the Ubuntu use of it is.
>
Ubuntu doesn't use Upstart on shutdown, it uses the plain-old sysv init scripts.

Oddly enough I don't see any bugs filed by you about startup issues?
Now, don't get me wrong, I'm not saying Ubuntu is perfect here - but
I'm not aware of any races that are Upstart's fault. If there are,
please file bugs! How else am I to fix them if I don't know about
them?

Scott
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