On Tue, Jul 29, 2014 at 08:05:25AM -0400, Tejun Heo wrote:

On Tue, Jul 29, 2014 at 09:56:37AM +0200, Peter Zijlstra wrote:

quoted

On Mon, Jul 28, 2014 at 01:55:17PM -0500, Christoph Lameter wrote:

quoted

On Fri, 25 Jul 2014, Sasha Levin wrote:

quoted

This patch doesn't interact well with my fuzzing setup. I'm seeing
the following:

[  490.446927] BUG: using __this_cpu_read() in preemptible [00000000] code: kworker/16:1/7368
[  490.447909] caller is __this_cpu_preempt_check+0x13/0x20

__this_cpu_read() from vmstat_update is only called from a kworker that
is bound to a single cpu. A false positive?

kworkers are never guaranteed to be so, its a 'feature' :/

It's because we don't distinguish work items which are per-cpu for
optimization and per-cpu for correctness and can't automatically flush
/ cancel / block per-cpu work items when a cpu goes down.  I like the
idea of distingushing them but it's gonna take a lot of auditing.

Just force flush on unplug and fix those that complain. No auditing
needed for that.

Any work item usage which requires per-cpu for correctness should
implement cpu down hook to flush in-flight work items and block
further issuance.  This hasn't changed from the beginning and was
necessary even before cmwq.

I think before cmwq we'd run into the broken affinity warning in the
scheduler.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>