On Thu, Oct 12, 2006 at 02:26:25PM -0700, Andrew Morton wrote:
> You've presumably run a kernel with these various things enabled. What
> happens? Does the kernel run really slowly? Does userspace collapse in a
> heap? Does it oops and die?
I don't feel much slowness with STACKTRACE & FRAME_POINTER and
enabling stacktrace filter. But with enabling STACK_UNWIND I feel
big latency on X. (There are two type of implementation of stacktrace
filter in it [1] using STACKTRACE with FRAME_POINTER, and [2] STACK_UNWIND)
I don't know why there is quite difference between simple STACKTRACE and
STACK_UNWIND. I'm about to try to use rb tree rather than linked list in
unwind.
In order to prevent from breaking other userspace programs and to
inject failures into only a specific code or process, process filter and
stacktrace filter are available. Without using them the system would be
almost unusable.
Now I'm stuck on the script in fault-injection.txt with random 700
modules. This script just tries to load/unload for all available kernel
modules. It usually get several oopses or CPU soft lockup now. It
seems that relatively large number of them involved around driver model
(drivers/base/*). (I hope recent large number of error handle fixes
especially by Jeff Garzik fix them)
> Also, one place where this infrastructure could be of benefit is in device
> drivers: simulate a bad sector on the disk, a pulled cable, a timeout
> reading from a status register, etc. If that works well and is useful then
> I can see us encouraging driver developers to wire up fault-injection in
> the major drivers.
>
> Hence it would be useful at some stage to go in and to actually do all this
> for a particular driver. As an example implementation for others to
> emulate and as a test for the fault-injection infrastructure itself - we
> may discover that new capabilities are needed as this work is done.
>
> I wouldn't say this is an urgent thing to be doing, but it is a logical
> next step..
Yes. I'm learning from md/faulty and scsi-debug module what they are
doing and how to integrate such kind of features in general form.
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