Re: [PATCH/RFC] remove irqs_disabled warning from local_bh_enable

Johannes Berg
2008-06-20T15:44:18Z

[-- Attachment #1: Type: text/plain, Size: 2499 bytes --]

On Fri, 2008-06-20 at 17:27 +0200, Ingo Molnar wrote:
> * Ingo Molnar <mingo@elte.hu> wrote:
>
> > > Subject: clean up and comment local_bh_enable code
> > >
> > > There's no need to use local_irq_save() over local_irq_disable() in
> > > the local_bh_enable code since it is a bug to call it with irqs
> > > disabled and do_softirq will enable irqs if there is any pending
> > > work. Consolidate the code from local_bh_enable and ..._ip to avoid
> > > having a disconnect between them in the warnings they trigger that
> > > is currently there. Also always trigger the warning on in_irq(), not
> > > just in the trace-irqflags case.
> >
> > applied to tip/core/softirq for testing, thanks Johannes.
>
> ok, -tip testing found that your patch triggers a new warning on an old
> testbox that uses 3c59x vortex and netlogging:
>
> ----->
> calling vortex_init+0x0/0xb0
> PCI: Found IRQ 10 for device 0000:00:0b.0
> PCI: Sharing IRQ 10 with 0000:00:0a.0
> PCI: Sharing IRQ 10 with 0000:00:0b.1
> 3c59x: Donald Becker and others.
> 0000:00:0b.0: 3Com PCI 3c556 Laptop Tornado at e0800400.
> PCI: Enabling bus mastering for device 0000:00:0b.0
> initcall vortex_init+0x0/0xb0 returned 0 after 47 msecs
> ...
> calling init_netconsole+0x0/0x1b0
> netconsole: local port 4444
> netconsole: local IP 10.0.1.9
> netconsole: interface eth0
> netconsole: remote port 4444
> netconsole: remote IP 10.0.1.16
> netconsole: remote ethernet address 00:19:xx:xx:xx:xx
> netconsole: device eth0 not up yet, forcing it
> eth0: setting half-duplex.
> eth0: setting full-duplex.
> ------------[ cut here ]------------
> WARNING: at kernel/softirq.c:137 local_bh_enable_ip+0xd1/0xe0()
> Pid: 1, comm: swapper Not tainted 2.6.26-rc6-tip #2091
> [<c0125ecf>] warn_on_slowpath+0x4f/0x70
> [<c0126834>] ? release_console_sem+0x1b4/0x1d0
> [<c0126d00>] ? vprintk+0x2a0/0x450

Now you can't printk in irq context any more?

vprintk:
/*
* Try to acquire and then immediately release the
* console semaphore. The release will do all the
* actual magic (print out buffers, wake up klogd,
* etc).
*
* The acquire_console_semaphore_for_printk() function
* will release 'logbuf_lock' regardless of whether it
* actually gets the semaphore or not.
*/
if (acquire_console_semaphore_for_printk(this_cpu))
release_console_sem();

johannes

[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 836 bytes --]