From: James Bottomley <James.Bottomley@HansenPartnership.com>
To: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Helge Deller <deller@gmx.de>, linux-parisc@vger.kernel.org
Subject: Re: [PATCH v1] parisc: Use for_each_console() helper
Date: Fri, 24 Jan 2020 09:59:48 -0800 [thread overview]
Message-ID: <1579888788.3001.26.camel@HansenPartnership.com> (raw)
In-Reply-To: <20200124173846.GL32742@smile.fi.intel.com>
On Fri, 2020-01-24 at 19:38 +0200, Andy Shevchenko wrote:
> On Fri, Jan 24, 2020 at 08:39:02AM -0800, James Bottomley wrote:
> > On Fri, 2020-01-24 at 18:07 +0200, Andy Shevchenko wrote:
> > > Replace open coded single-linked list iteration loop with
> > > for_each_console()
> > > helper in use.
> > > - while ((console = console_drivers) != NULL)
> > > - unregister_console(console_drivers);
> > > + for_each_console(console)
> > > + unregister_console(console);
> >
> > This is wrong. The old formulation iterates correctly in the face
> > of element removal. for_each_console is defined:
> >
> > #define for_each_console(con) \
> > for (con = console_drivers; con != NULL; con = con->next)
> >
> > So it's not safe for any iteration that alters the list elements.
>
> Ah, I see. In this case we need to keep a pointer to the next
> element. Though, the original code assumes that console_drivers after
> unregistration will be promoted to the next element. Do we have this
> assumption solid?
Yes, the original code simply removes the head until the list is empty.
That's a recognized way of emptying any list while letting the remove
code take care of the locking ... it works because parisc doesn't have
a braille console.
James
next prev parent reply other threads:[~2020-01-24 17:59 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-24 16:07 [PATCH v1] parisc: Use for_each_console() helper Andy Shevchenko
2020-01-24 16:39 ` James Bottomley
2020-01-24 17:38 ` Andy Shevchenko
2020-01-24 17:59 ` James Bottomley [this message]
2020-01-25 10:25 ` Andy Shevchenko
2020-01-27 8:48 ` Helge Deller
2020-01-27 9:47 ` Andy Shevchenko
2020-01-30 14:07 ` Petr Mladek
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