Messages in this thread | | | Date | Tue, 18 Nov 2008 07:38:19 +0000 | From | Jarek Poplawski <> | Subject | Re: [PATCH] softirq: Use local_irq_save() in local_bh_enable() |
| |
On Mon, Nov 17, 2008 at 05:16:17PM +0100, Ingo Molnar wrote: > > * Jarek Poplawski <jarkao2@gmail.com> wrote: > > > This report: http://marc.info/?l=linux-netdev&m=122599341430090&w=2 > > shows local_bh_enable() is used in the wrong context (irqs > > disabled). It happens when a usual network receive path is called by > > netconsole, which simply turns off irqs around this all. Probably > > this is wrong, but it worked like this long time, and it's not > > trivial to fix this. > > > > Anyway, a commit 0f476b6d91a1395bda6464e653ce66ea9bea7167 "softirq: > > remove irqs_disabled warning from local_bh_enable" can break things > > after changing from local_irq_save() to local_irq_disable(). Before > > this commit there was only a warning, now a lockup is possible, so > > it could be treated as a regression. This patch reverts the change > > in irqs. > > hm, but calling local_bh_enable() with hardirqs off is a bug. It might > be a long-standing bug, but it can cause lockups even with that change > reverted: when we process softirqs in local_bh_enable().
I think it's what they call a regression: this is a long-standing bug, and this commit doesn't fix this, but can cause additional lockups.
> So why not > fix the bug instead?
It's not about instead: this bug could be fixed as well (if somebody knows how to do it "properly" without hacks like: if (!in_irq()) local_bh_disable(); etc.; but, I guess, the network code has more such bh disabling).
Jarek P.
| |