Messages in this thread | | | Date | Tue, 18 Aug 2020 14:52:18 +0200 | From | Petr Mladek <> | Subject | Re: [PATCH] uart:8250: change lock order in serial8250_do_startup() |
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On Fri 2020-08-14 12:59:28, Andy Shevchenko wrote: > On Fri, Aug 14, 2020 at 10:38:02AM +0900, Sergey Senozhatsky wrote: > > We have a number of "uart.port->desc.lock vs desc.lock->uart.port" > > lockdep reports coming from 8250 driver; this causes a bit of trouble > > to people, so let's fix it. > > > > I guess we may add some tags here > > Fixes: 768aec0b5bcc ("serial: 8250: fix shared interrupts issues with SMP and RT kernels") > Reported-by: Guenter Roeck <linux@roeck-us.net> > Reported-by: Raul Rangel <rrangel@google.com> > BugLink: https://bugs.chromium.org/p/chromium/issues/detail?id=1114800 > Link: https://lore.kernel.org/lkml/CAHQZ30BnfX+gxjPm1DUd5psOTqbyDh4EJE=2=VAMW_VDafctkA@mail.gmail.com/T/#u
"Link:" tag should point to the mail that is applied using git am. I am not sure if there is a tag for related discussion in another mail threads.
A solution might be to add a comment like:
This solution has been discussed in several threads: https://lore.kernel.org/lkml/CAHQZ30BnfX+gxjPm1DUd5psOTqbyDh4EJE=2=VAMW_VDafctkA@mail.gmail.com/T/#u https://lore.kernel.org/lkml/20200812154813.GA46894@roeck-us.net/#t
> > --- a/drivers/tty/serial/8250/8250_port.c > > +++ b/drivers/tty/serial/8250/8250_port.c > > @@ -2275,6 +2275,11 @@ int serial8250_do_startup(struct uart_port *port) > > > > if (port->irq && !(up->port.flags & UPF_NO_THRE_TEST)) { > > unsigned char iir1; > > > + bool irq_shared = up->port.irqflags & IRQF_SHARED; > > I'm wondering why we need a temporary variable? This flag is not supposed to be > changed in between, can we leave original conditionals? > > Nevertheless I noticed an inconsistency of the dereference of the flags which > seems to be brough by dfe42443ea1d ("serial: reduce number of indirections in > 8250 code"). > > I think we can stick with newer: > > if (port->irqflags & IRQF_SHARED)
Sounds reasonable to me.
Andy proposed many changes. Sergey, could you please send v2?
Best Regards, Petr
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