On 06/17/2011 12:08 AM, Pavel Roskin wrote:
On 06/16/2011 06:22 AM, Stanislaw Gruszka wrote:
Hi Pavel
On Wed, Jun 15, 2011 at 06:02:52PM -0400, Pavel Roskin wrote:
WARN_ON is not enough, as we cannot return a valid index, and the
callers will use whatever we return, causing a cascade of oopses and
eventually a panic.
We have fedora bug (https://bugzilla.redhat.com/show_bug.cgi?id=702627)
where only that warning is generated, and system works further (at least
bug reporter did not mention about it's hang). When moving to BUG(),
system from user perspective will simply hang, what is much worse.
I think, we should rather fix callers to be prepared and recover itself
when rate_lowest_index fail. Of course fixing real bug(s) that cause
rate index is not found would be best.
In my case, I was able to restart the system by sysrq when using BUG_ON,
but the system would hang hard with WARN_ON. I think continuing after
returning an invalid index is wrong. It will lead to memory corruption
that could in turn lead to corruption of the filesystem.
I think it is generally a bad idea to use BUG_ON as a solution. As
Stanislaw indicated there are platforms which can continue without a
hang so you are regressing those. Regarding your patch I think the
-EINVAL is good to have, but leave the WARN_ON.
Gr. AvS
--
Almost nobody dances sober, unless they happen to be insane.
-- H.P. Lovecraft --
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