From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hans de Goede Date: Thu, 19 Jul 2018 11:43:17 +0000 Subject: Re: [PATCH v2 1/1] fbdev/core: Disable console-lock warnings when fb.lockless_register_fb is set Message-Id: <867bcf01-52c6-cb50-6573-73f2d5c8dcab@redhat.com> List-Id: References: <20180718093002.4596-1-tzimmermann@suse.de> <20180718093002.4596-2-tzimmermann@suse.de> <20180719085303.mkxu7i7zl4suybcz@pathway.suse.cz> In-Reply-To: <20180719085303.mkxu7i7zl4suybcz@pathway.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Petr Mladek , Thomas Zimmermann Cc: linux-fbdev@vger.kernel.org, sergey.senozhatsky.work@gmail.com, b.zolnierkie@samsung.com, dri-devel@lists.freedesktop.org, sergey.senozhatsky@gmail.com, rostedt@goodmis.org, akpm@linux-foundation.org Hi, On 19-07-18 10:53, Petr Mladek wrote: > On Wed 2018-07-18 11:30:02, Thomas Zimmermann wrote: >> If the console is unlocked during registration, the console subsystem >> generates significant amounts of warnings, which obfuscate actual >> debugging messages. Setting ignore_console_lock_warning while debugging >> console registration avoid the noise. >> >> v2: >> - restore ignore_console_lock_warning if lock_fb_info() fails >> >> Signed-off-by: Thomas Zimmermann >> --- >> drivers/video/fbdev/core/fbmem.c | 15 +++++++++++---- >> 1 file changed, 11 insertions(+), 4 deletions(-) >> >> diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c >> index 9e2f9d3c760e..432c26eeabfb 100644 >> --- a/drivers/video/fbdev/core/fbmem.c >> +++ b/drivers/video/fbdev/core/fbmem.c >> @@ -1627,6 +1627,7 @@ static int do_register_framebuffer(struct fb_info *fb_info) >> int i, ret; >> struct fb_event event; >> struct fb_videomode mode; >> + bool saved_ignore_console_lock_warning = ignore_console_lock_warning; > > Hmm, this approach is racy if there are other users > saving/setting/restoring ignore_console_lock_warning in parallel. > I mean that this works only when the entire safe/set/restore > operation is nested or sequential. > > We might need another approach if there are more users, > e.g. use an atomic counter for ignore_console_lock_warning. I noticed this would be racy too, but this only gets used when console-locking should be disabled when registering fbdev-s for debugging purposes at which point everything console related is racy already anyways, so I think this is fine as is. > On the other hand, I wonder if there ever will be other user. > Also it is "just" for debugging. We could keep it simple for now. > It might be enough to add a comment into include/linux/console.h, > something like: Ack, lets keep this simple / as is in v2 of the patch. Regards, Hans > > /* > * Set ignore_console_lock_warning to true if you need to quiet > * WARN_CONSOLE_UNLOCKED() for debugging purposes. Might need > * another approach if manipulated by more users in parallel. > */ > > Best Regards, > Petr >