Re: Reporting bugs and bisection

On Sun, Apr 13, 2008 at 11:24:41PM -0700, Andrew Morton wrote:

In addition to obvious "we need testing and something better than bugzilla to keep track of bugs"? Real review of code in tree and patches getting into the tree.

And the latter part _must_ be done on each entry point. Any git tree that acts as injection point really needs a working mechanism of some sort that would do that; afterwards it's too late, since review of the stuff getting into mainline on a massive merge is sadly impractical.

I don't know any formal mechanism that could take care of that; no more than making sure that no backdoors are injected into the tree. It really has to be a matter of trust for tree maintainers and community around the subsystem.

Git is damn good at killing the merge bottleneck. Too good, since it hides the review bottleneck. And we get equivalents of self-selected communities that had been problem for "here's our CVS, here's monthly dump from it, apply" kind of setups. It _is_ better, since one can get to commit history (modulo interesting issues with merge nodes and conflict resolution). But in practice it's not good enough - the patches going in during a merge (especially for a tree that collects from secondaries) are not visible enough. And it's too late at that point, since one has to do something monumentally ugly to get Linus revert a large merge. On the scale of Great IDE Mess in 2.5...

linux-next might help with the last part, but I don't think it really deals with the first one. It certainly helps to some extent, but...

We need higher S/N on l-k. We need people looking into the subsystem trees as those grow and causing a stench when bad things are found, with design issues getting brought to l-k if nothing else helps. We need tree maintainers understanding that review, including out-of-community one, is needed (the need of testing is generally better understood - I _hope_).

We need more people reading the fscking source. Subsystem by subsystem. Without assumption that code is not broken. With mechanism collating the questions asked and answers given. Ideally we need growing documentation of core subsystems and data structures, with explicit goal of helping reviewers new to an area to find their way around it. And yes, I'm guilty of procrastinating on that - several half-finished pieces on VFS-related stuff are sitting locally ;-/

We need gregkh to get real and stop assuming that two Signed-off-by are equivalent to "reviewed at least twice", while we are at it ;-)

We need people to realize that warnings are useful as triage tools - not as "Ug see warning. Warning bad. Ug fix that line. Warning go away. Ug changeset count grow. Ug happy.", but as machine-assisted part of finding confused areas of code. With human combining signals from different warnings to get statistically useful triage strategies (note that aforementioned making gcc/sparse/whatnot to STFU by local change has a lovely potential of distorting those signals and actually _hiding_ crap code).

Maybe we need a list a-la linux-arch for tree maintainers to coordinate stuff - obviously open not only for those.

We really need to get around to doing triage of remaining stuff in -mm, BTW - again, guilty for not getting through such on VFS-related stuff in there. Hopefully linux-next trees will eventually vacuum most of the pile in...

As for the bug that got this thread started... I'd say that asking to bisect was reasonable in this particular case. The following DSW mixed into the thread very soon went the way of all DSW (OK, it hadn't godwinated yet, at least in the parts I've seen, so there's still way to go, but...)