Messages in this thread | | | Date | Tue, 28 Nov 2006 18:18:11 +0900 | From | Akinobu Mita <> | Subject | Re: [PATCH 2/2 -mm] fault-injection: lightweight code-coverage maximizer |
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On Mon, Nov 27, 2006 at 11:51:30PM -0800, Don Mullis wrote: > Allow all non-unique call stacks, as judged by pushed sequence of EIPs, > to be to be ignored as failure candidates. > > Upon keying in > echo 1 >probability > echo 3 >verbose > echo -1 >times > a few dozen stacks are printk'ed, then system responsiveness > recovers to normal. Similarly, starting a non-trivial program > will print a few stacks before responsiveness recovers.
What kind of test did you do?
> Intent is to make code-coverage-maximizing test lightweight, perhaps > light enough to remain enabled during the course of the developer's > interactive testing of new code. > > Enabled by default. (/debug/fail*/stacktrace-depth > 0)
This doesn't maximize code coverage. It makes fault-injector reject any failures which have same stacktrace before.
So it should not be default.
> +static bool fail_uniquestack(struct fault_attr *attr) > +{ > + u32 oldhash; > + u32 newhash; > + uint offset = 0; > + > + newhash = unique_stack_p(attr); > + > + for ( oldhash = newhash; oldhash != 0; offset++) { > + oldhash = atomic_xchg( > + &attr->uniquestack_hash_table[ > + (newhash+offset)%ARRAY_SIZE(attr->uniquestack_hash_table)], > + oldhash); > + if (oldhash == newhash) > + return false; > + if (offset >= ARRAY_SIZE(attr->uniquestack_hash_table)) { > + printk(KERN_NOTICE > + "FAULT_INJECTION: table overflow -- " > + "fault injection disabled\n"); > + return false; > + } > + }
Updating array in this way is not safe (SMP or interrupt).
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