On Wed, Jun 26, 2019 at 1:27 AM Takashi Iwai <tiwai@xxxxxxx> wrote: > > On Tue, 25 Jun 2019 23:54:18 +0200, > Evan Green wrote: > > > > The normal flow through the widget sysfs codepath is that > > snd_hdac_refresh_widgets() is called once without the sysfs bool set > > to set up codec->num_nodes and friends, then another time with the > > bool set to actually allocate all the sysfs widgets. However, during > > the first time allocation, hda_widget_sysfs_reinit() ignores the new > > num_nodes passed in via parameter and just calls hda_widget_sysfs_init(), > > using whatever was in codec->num_nodes before the update. This is not > > correct in cases where num_nodes changes. Here's an example: > > > > Sometime earlier: > > snd_hdac_refresh_widgets(hdac, false) > > sets codec->num_nodes to 2, widgets is still not allocated > > > > Now: > > snd_hdac_refresh_widgets(hdac, true) > > hda_widget_sysfs_reinit(num_nodes=7) > > hda_widget_sysfs_init() > > widget_tree_create() > > alloc(codec->num_nodes) // this is still 2 > > codec->num_nodes = 7 > > > > Pass num_nodes and start_nid down into widget_tree_create() so that > > the right number of nodes are allocated in all cases. > > > > Signed-off-by: Evan Green <evgreen@xxxxxxxxxxxx> > > Thanks for the patch. That's indeed a problem, but I guess a simpler > approach is just to return if sysfs didn't exist. If the sysfs > entries aren't present at the second call with sysfs=true, it implies > that the codec object will be exposed anyway later, and the sysfs will > be created there. So, something like below would work instead? Hi Takashi, Thanks for taking a look. I'm not sure you'd want to do that because then you end up returning from sysfs_reinit without having allocated any of the sysfs widgets. You'd be relying on the implicit behavior that another call to init is coming later (despite having updated num_nodes and start node), which is difficult to follow and easy to break. In my opinion the slight bit of extra diffs is well worth the clarity of having widget_tree_create always allocate the correct start/count. Actually, in looking at the widget lock patch, I don't think it's sufficient either. It adds a lock around sysfs_reinit, but the setting of codec->num_nodes and codec->start_nid is unprotected by the lock. So you could have the two threads politely serialize through sysfs_reinit, but then get reordered before setting codec->num_nodes, landing you with an array whose length doesn't match num_nodes. Let me craft up an additional patch to fix the locking. -Evan > > > thanks, > > Takashi > > --- a/sound/hda/hdac_sysfs.c > +++ b/sound/hda/hdac_sysfs.c > @@ -428,7 +428,7 @@ int hda_widget_sysfs_reinit(struct hdac_device *codec, > int i; > > if (!codec->widgets) > - return hda_widget_sysfs_init(codec); > + return 0; > > tree = kmemdup(codec->widgets, sizeof(*tree), GFP_KERNEL); > if (!tree) _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx https://mailman.alsa-project.org/mailman/listinfo/alsa-devel
