| Message ID | 20190524085354.27411-26-daniel.vetter@ffwll.ch (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | fbcon notifier begone! | expand |
Hi Daniel. On Fri, May 24, 2019 at 10:53:46AM +0200, Daniel Vetter wrote: > There's a callchain of: > > fbcon_fb_blaned -> do_(un)blank_screen -> consw->con_blank ^^^^^^ Spelling error - as this is a callchain it would be good to have it fixed. Patch itself looks fine. Sam > -> fbcon_blank -> fb_blank > > Things don't go horribly wrong because the BKL console_lock safes the > day, but that's about it. And the seeming recursion is broken in 2 > ways: > - Starting from the fbdev ioctl we set FBINFO_MISC_USEREVENT, which > tells the fbcon_blank code to not call fb_blank. This was required > to not deadlock when recursing on the fb_notifier_chain mutex. > - Starting from the con_blank hook we're getting saved by the > console_blanked checks in do_blank/unblank_screen. Or at least > that's my theory. > > Anyway, recursion isn't awesome, so let's stop it. Breaking the > recursion avoids the need to be in the FBINFO_MISC_USEREVENT critical > section, so lets move it out of that too. > > The astute reader will notice that fb_blank seems to require > lock_fb_info(), which the fbcon code seems to ignore. I have no idea > how to fix that problem, so let's keep ignoring it. > > v2: I forgot the sysfs blanking code. > > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com> > Cc: Daniel Vetter <daniel.vetter@ffwll.ch> > Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com> > Cc: "Michał Mirosław" <mirq-linux@rere.qmqm.pl> > Cc: Peter Rosin <peda@axentia.se> > Cc: Hans de Goede <hdegoede@redhat.com> > Cc: Mikulas Patocka <mpatocka@redhat.com> > Cc: Rob Clark <robdclark@gmail.com> > --- > drivers/video/fbdev/core/fbmem.c | 4 +++- > drivers/video/fbdev/core/fbsysfs.c | 8 ++++++-- > 2 files changed, 9 insertions(+), 3 deletions(-) > > diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c > index 9366fbe99a58..d6713dce9e31 100644 > --- a/drivers/video/fbdev/core/fbmem.c > +++ b/drivers/video/fbdev/core/fbmem.c > @@ -1068,7 +1068,6 @@ fb_blank(struct fb_info *info, int blank) > event.data = ␣ > > early_ret = fb_notifier_call_chain(FB_EARLY_EVENT_BLANK, &event); > - fbcon_fb_blanked(info, blank); > > if (info->fbops->fb_blank) > ret = info->fbops->fb_blank(blank, info); > @@ -1198,6 +1197,9 @@ static long do_fb_ioctl(struct fb_info *info, unsigned int cmd, > info->flags |= FBINFO_MISC_USEREVENT; > ret = fb_blank(info, arg); > info->flags &= ~FBINFO_MISC_USEREVENT; > + > + /* might again call into fb_blank */ > + fbcon_fb_blanked(info, arg); > unlock_fb_info(info); > console_unlock(); > break; > diff --git a/drivers/video/fbdev/core/fbsysfs.c b/drivers/video/fbdev/core/fbsysfs.c > index 5f329278e55f..252d4f52d2a5 100644 > --- a/drivers/video/fbdev/core/fbsysfs.c > +++ b/drivers/video/fbdev/core/fbsysfs.c > @@ -18,6 +18,7 @@ > #include <linux/kernel.h> > #include <linux/slab.h> > #include <linux/fb.h> > +#include <linux/fbcon.h> > #include <linux/console.h> > #include <linux/module.h> > > @@ -305,12 +306,15 @@ static ssize_t store_blank(struct device *device, > { > struct fb_info *fb_info = dev_get_drvdata(device); > char *last = NULL; > - int err; > + int err, arg; > > + arg = simple_strtoul(buf, &last, 0); > console_lock(); > fb_info->flags |= FBINFO_MISC_USEREVENT; > - err = fb_blank(fb_info, simple_strtoul(buf, &last, 0)); > + err = fb_blank(fb_info, arg); > fb_info->flags &= ~FBINFO_MISC_USEREVENT; > + /* might again call into fb_blank */ > + fbcon_fb_blanked(fb_info, arg); > console_unlock(); > if (err < 0) > return err; > -- > 2.20.1 > > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/dri-devel
diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c index 9366fbe99a58..d6713dce9e31 100644 --- a/drivers/video/fbdev/core/fbmem.c +++ b/drivers/video/fbdev/core/fbmem.c @@ -1068,7 +1068,6 @@ fb_blank(struct fb_info *info, int blank) event.data = ␣ early_ret = fb_notifier_call_chain(FB_EARLY_EVENT_BLANK, &event); - fbcon_fb_blanked(info, blank); if (info->fbops->fb_blank) ret = info->fbops->fb_blank(blank, info); @@ -1198,6 +1197,9 @@ static long do_fb_ioctl(struct fb_info *info, unsigned int cmd, info->flags |= FBINFO_MISC_USEREVENT; ret = fb_blank(info, arg); info->flags &= ~FBINFO_MISC_USEREVENT; + + /* might again call into fb_blank */ + fbcon_fb_blanked(info, arg); unlock_fb_info(info); console_unlock(); break; diff --git a/drivers/video/fbdev/core/fbsysfs.c b/drivers/video/fbdev/core/fbsysfs.c index 5f329278e55f..252d4f52d2a5 100644 --- a/drivers/video/fbdev/core/fbsysfs.c +++ b/drivers/video/fbdev/core/fbsysfs.c @@ -18,6 +18,7 @@ #include <linux/kernel.h> #include <linux/slab.h> #include <linux/fb.h> +#include <linux/fbcon.h> #include <linux/console.h> #include <linux/module.h> @@ -305,12 +306,15 @@ static ssize_t store_blank(struct device *device, { struct fb_info *fb_info = dev_get_drvdata(device); char *last = NULL; - int err; + int err, arg; + arg = simple_strtoul(buf, &last, 0); console_lock(); fb_info->flags |= FBINFO_MISC_USEREVENT; - err = fb_blank(fb_info, simple_strtoul(buf, &last, 0)); + err = fb_blank(fb_info, arg); fb_info->flags &= ~FBINFO_MISC_USEREVENT; + /* might again call into fb_blank */ + fbcon_fb_blanked(fb_info, arg); console_unlock(); if (err < 0) return err;
There's a callchain of: fbcon_fb_blaned -> do_(un)blank_screen -> consw->con_blank -> fbcon_blank -> fb_blank Things don't go horribly wrong because the BKL console_lock safes the day, but that's about it. And the seeming recursion is broken in 2 ways: - Starting from the fbdev ioctl we set FBINFO_MISC_USEREVENT, which tells the fbcon_blank code to not call fb_blank. This was required to not deadlock when recursing on the fb_notifier_chain mutex. - Starting from the con_blank hook we're getting saved by the console_blanked checks in do_blank/unblank_screen. Or at least that's my theory. Anyway, recursion isn't awesome, so let's stop it. Breaking the recursion avoids the need to be in the FBINFO_MISC_USEREVENT critical section, so lets move it out of that too. The astute reader will notice that fb_blank seems to require lock_fb_info(), which the fbcon code seems to ignore. I have no idea how to fix that problem, so let's keep ignoring it. v2: I forgot the sysfs blanking code. Signed-off-by: Daniel Vetter <daniel.vetter@intel.com> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com> Cc: "Michał Mirosław" <mirq-linux@rere.qmqm.pl> Cc: Peter Rosin <peda@axentia.se> Cc: Hans de Goede <hdegoede@redhat.com> Cc: Mikulas Patocka <mpatocka@redhat.com> Cc: Rob Clark <robdclark@gmail.com> --- drivers/video/fbdev/core/fbmem.c | 4 +++- drivers/video/fbdev/core/fbsysfs.c | 8 ++++++-- 2 files changed, 9 insertions(+), 3 deletions(-)