fbcon: Use delayed work for cursor

Allows us to delete a bunch of hand-rolled stuff using a timer plus a
separate work). Also to simplify the code we initialize the
cursor_work completely when we allocate the fbcon_ops structure,
instead of trying to cope with console re-initialization.

The motiviation here is that fbcon code stops using the fb_info.queue,
which helps with locking issues around cleanup and all that in a later
patch.

Also note that this allows us to ditch the hand-rolled work cleanup in
fbcon_exit - we already call fbcon_del_cursor_timer, which takes care
of everything. Plus this was racy anyway.

v2:
- Only INIT_DELAYED_WORK when kzalloc succeeded (Tetsuo)
- Explain that we replace both the timer and a work with the combined
  delayed_work (Javier)
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Claudio Suarez <cssk@net-c.es>
Cc: Du Cheng <ducheng2@gmail.com>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Link: https://patchwork.freedesktop.org/patch/msgid/20220405210335.3434130-7-daniel.vetter@ffwll.ch

drivers/video/fbdev/core/fbcon.c

@@ -350,8 +350,8 @@ static int get_color(struct vc_data *vc, struct fb_info *info,
 
 static void fb_flashcursor(struct work_struct *work)
 {
-	struct fb_info *info = container_of(work, struct fb_info, queue);
-	struct fbcon_ops *ops = info->fbcon_par;
+	struct fbcon_ops *ops = container_of(work, struct fbcon_ops, cursor_work.work);
+	struct fb_info *info;
 	struct vc_data *vc = NULL;
 	int c;
 	int mode;
@@ -364,7 +364,10 @@ static void fb_flashcursor(struct work_struct *work)
 	if (ret == 0)
 		return;
 
-	if (ops && ops->currcon != -1)
+	/* protected by console_lock */
+	info = ops->info;
+
+	if (ops->currcon != -1)
 		vc = vc_cons[ops->currcon].d;
 
 	if (!vc || !con_is_visible(vc) ||
@@ -380,42 +383,25 @@ static void fb_flashcursor(struct work_struct *work)
 	ops->cursor(vc, info, mode, get_color(vc, info, c, 1),
 		    get_color(vc, info, c, 0));
 	console_unlock();
-}
 
-static void cursor_timer_handler(struct timer_list *t)
-{
-	struct fbcon_ops *ops = from_timer(ops, t, cursor_timer);
-	struct fb_info *info = ops->info;
-
-	queue_work(system_power_efficient_wq, &info->queue);
-	mod_timer(&ops->cursor_timer, jiffies + ops->cur_blink_jiffies);
+	queue_delayed_work(system_power_efficient_wq, &ops->cursor_work,
+			   ops->cur_blink_jiffies);
 }
 
-static void fbcon_add_cursor_timer(struct fb_info *info)
+static void fbcon_add_cursor_work(struct fb_info *info)
 {
 	struct fbcon_ops *ops = info->fbcon_par;
 
-	if ((!info->queue.func || info->queue.func == fb_flashcursor) &&
-	    !(ops->flags & FBCON_FLAGS_CURSOR_TIMER) &&
-	    !fbcon_cursor_noblink) {
-		if (!info->queue.func)
-			INIT_WORK(&info->queue, fb_flashcursor);
-
-		timer_setup(&ops->cursor_timer, cursor_timer_handler, 0);
-		mod_timer(&ops->cursor_timer, jiffies + ops->cur_blink_jiffies);
-		ops->flags |= FBCON_FLAGS_CURSOR_TIMER;
-	}
+	if (!fbcon_cursor_noblink)
+		queue_delayed_work(system_power_efficient_wq, &ops->cursor_work,
+				   ops->cur_blink_jiffies);
 }
 
-static void fbcon_del_cursor_timer(struct fb_info *info)
+static void fbcon_del_cursor_work(struct fb_info *info)
 {
 	struct fbcon_ops *ops = info->fbcon_par;
 
-	if (info->queue.func == fb_flashcursor &&
-	    ops->flags & FBCON_FLAGS_CURSOR_TIMER) {
-		del_timer_sync(&ops->cursor_timer);
-		ops->flags &= ~FBCON_FLAGS_CURSOR_TIMER;
-	}
+	cancel_delayed_work_sync(&ops->cursor_work);
 }
 
 #ifndef MODULE
@@ -717,6 +703,8 @@ static int con2fb_acquire_newinfo(struct vc_data *vc, struct fb_info *info,
 	}
 
 	if (!err) {
+		INIT_DELAYED_WORK(&ops->cursor_work, fb_flashcursor);
+
 		ops->cur_blink_jiffies = HZ / 5;
 		ops->info = info;
 		info->fbcon_par = ops;
@@ -751,7 +739,7 @@ static int con2fb_release_oldinfo(struct vc_data *vc, struct fb_info *oldinfo,
 	}
 
 	if (!err) {
-		fbcon_del_cursor_timer(oldinfo);
+		fbcon_del_cursor_work(oldinfo);
 		kfree(ops->cursor_state.mask);
 		kfree(ops->cursor_data);
 		kfree(ops->cursor_src);
@@ -867,7 +855,7 @@ static int set_con2fb_map(int unit, int newidx, int user)
 				 logo_shown != FBCON_LOGO_DONTSHOW);
 
 		if (!found)
-			fbcon_add_cursor_timer(info);
+			fbcon_add_cursor_work(info);
 		con2fb_map_boot[unit] = newidx;
 		con2fb_init_display(vc, info, unit, show_logo);
 	}
@@ -964,6 +952,8 @@ static const char *fbcon_startup(void)
 		return NULL;
 	}
 
+	INIT_DELAYED_WORK(&ops->cursor_work, fb_flashcursor);
+
 	ops->currcon = -1;
 	ops->graphics = 1;
 	ops->cur_rotate = -1;
@@ -1006,7 +996,7 @@ static const char *fbcon_startup(void)
 		 info->var.yres,
 		 info->var.bits_per_pixel);
 
-	fbcon_add_cursor_timer(info);
+	fbcon_add_cursor_work(info);
 	return display_desc;
 }
 
@@ -1194,7 +1184,7 @@ static void fbcon_deinit(struct vc_data *vc)
 		goto finished;
 
 	if (con_is_visible(vc))
-		fbcon_del_cursor_timer(info);
+		fbcon_del_cursor_work(info);
 
 	ops->flags &= ~FBCON_FLAGS_INIT;
 finished:
@@ -1320,9 +1310,9 @@ static void fbcon_cursor(struct vc_data *vc, int mode)
 		return;
 
 	if (vc->vc_cursor_type & CUR_SW)
-		fbcon_del_cursor_timer(info);
+		fbcon_del_cursor_work(info);
 	else
-		fbcon_add_cursor_timer(info);
+		fbcon_add_cursor_work(info);
 
 	ops->cursor_flash = (mode == CM_ERASE) ? 0 : 1;
 
@@ -2132,14 +2122,14 @@ static int fbcon_switch(struct vc_data *vc)
 		}
 
 		if (old_info != info)
-			fbcon_del_cursor_timer(old_info);
+			fbcon_del_cursor_work(old_info);
 	}
 
 	if (fbcon_is_inactive(vc, info) ||
 	    ops->blank_state != FB_BLANK_UNBLANK)
-		fbcon_del_cursor_timer(info);
+		fbcon_del_cursor_work(info);
 	else
-		fbcon_add_cursor_timer(info);
+		fbcon_add_cursor_work(info);
 
 	set_blitting_type(vc, info);
 	ops->cursor_reset = 1;
@@ -2247,9 +2237,9 @@ static int fbcon_blank(struct vc_data *vc, int blank, int mode_switch)
 
 	if (mode_switch || fbcon_is_inactive(vc, info) ||
 	    ops->blank_state != FB_BLANK_UNBLANK)
-		fbcon_del_cursor_timer(info);
+		fbcon_del_cursor_work(info);
 	else
-		fbcon_add_cursor_timer(info);
+		fbcon_add_cursor_work(info);
 
 	return 0;
 }
@@ -3181,7 +3171,7 @@ static ssize_t show_cursor_blink(struct device *device,
 	if (!ops)
 		goto err;
 
-	blink = (ops->flags & FBCON_FLAGS_CURSOR_TIMER) ? 1 : 0;
+	blink = delayed_work_pending(&ops->cursor_work);
 err:
 	console_unlock();
 	return snprintf(buf, PAGE_SIZE, "%d\n", blink);
@@ -3210,10 +3200,10 @@ static ssize_t store_cursor_blink(struct device *device,
 
 	if (blink) {
 		fbcon_cursor_noblink = 0;
-		fbcon_add_cursor_timer(info);
+		fbcon_add_cursor_work(info);
 	} else {
 		fbcon_cursor_noblink = 1;
-		fbcon_del_cursor_timer(info);
+		fbcon_del_cursor_work(info);
 	}
 
 err:
@@ -3314,15 +3304,9 @@ static void fbcon_exit(void)
 #endif
 
 	for_each_registered_fb(i) {
-		int pending = 0;
-
 		mapped = 0;
 		info = registered_fb[i];
 
-		if (info->queue.func)
-			pending = cancel_work_sync(&info->queue);
-		pr_debug("fbcon: %s pending work\n", (pending ? "canceled" : "no"));
-
 		for (j = first_fb_vc; j <= last_fb_vc; j++) {
 			if (con2fb_map[j] == i) {
 				mapped = 1;
@@ -3338,15 +3322,12 @@ static void fbcon_exit(void)
 			if (info->fbcon_par) {
 				struct fbcon_ops *ops = info->fbcon_par;
 
-				fbcon_del_cursor_timer(info);
+				fbcon_del_cursor_work(info);
 				kfree(ops->cursor_src);
 				kfree(ops->cursor_state.mask);
 				kfree(info->fbcon_par);
 				info->fbcon_par = NULL;
 			}
-
-			if (info->queue.func == fb_flashcursor)
-				info->queue.func = NULL;
 		}
 	}
 }

drivers/video/fbdev/core/fbcon.h

@@ -14,11 +14,11 @@
 #include <linux/types.h>
 #include <linux/vt_buffer.h>
 #include <linux/vt_kern.h>
+#include <linux/workqueue.h>
 
 #include <asm/io.h>
 
 #define FBCON_FLAGS_INIT         1
-#define FBCON_FLAGS_CURSOR_TIMER 2
 
    /*
     *    This is the interface between the low-level console driver and the
@@ -68,7 +68,7 @@ struct fbcon_ops {
 	int  (*update_start)(struct fb_info *info);
 	int  (*rotate_font)(struct fb_info *info, struct vc_data *vc);
 	struct fb_var_screeninfo var;  /* copy of the current fb_var_screeninfo */
-	struct timer_list cursor_timer; /* Cursor timer */
+	struct delayed_work cursor_work; /* Cursor timer */
 	struct fb_cursor cursor_state;
 	struct fbcon_display *p;
 	struct fb_info *info;