From 3a41c5dbe8bc396a7fb16ca8739e945bb003342e Mon Sep 17 00:00:00 2001 From: Gu Zheng Date: Tue, 5 Nov 2013 18:00:57 +0800 Subject: fb: reorder the lock sequence to fix potential dead lock Following commits: 50e244cc79 fb: rework locking to fix lock ordering on takeover e93a9a8687 fb: Yet another band-aid for fixing lockdep mess 054430e773 fbcon: fix locking harder reworked locking to fix related lock ordering on takeover, and introduced console_lock into fbmem, but it seems that the new lock sequence(fb_info->lock ---> console_lock) is against with the one in console_callback(console_lock ---> fb_info->lock), and leads to a potential dead lock as following: [ 601.079000] ====================================================== [ 601.079000] [ INFO: possible circular locking dependency detected ] [ 601.079000] 3.11.0 #189 Not tainted [ 601.079000] ------------------------------------------------------- [ 601.079000] kworker/0:3/619 is trying to acquire lock: [ 601.079000] (&fb_info->lock){+.+.+.}, at: [] lock_fb_info+0x26/0x60 [ 601.079000] but task is already holding lock: [ 601.079000] (console_lock){+.+.+.}, at: [] console_callback+0x13/0x160 [ 601.079000] which lock already depends on the new lock. [ 601.079000] the existing dependency chain (in reverse order) is: [ 601.079000] -> #1 (console_lock){+.+.+.}: [ 601.079000] [] lock_acquire+0xa1/0x140 [ 601.079000] [] console_lock+0x77/0x80 [ 601.079000] [] register_framebuffer+0x1d8/0x320 [ 601.079000] [] efifb_probe+0x408/0x48f [ 601.079000] [] platform_drv_probe+0x43/0x80 [ 601.079000] [] driver_probe_device+0x8b/0x390 [ 601.079000] [] __driver_attach+0xab/0xb0 [ 601.079000] [] bus_for_each_dev+0x5d/0xa0 [ 601.079000] [] driver_attach+0x1e/0x20 [ 601.079000] [] bus_add_driver+0x117/0x290 [ 601.079000] [] driver_register+0x7a/0x170 [ 601.079000] [] __platform_driver_register+0x4a/0x50 [ 601.079000] [] platform_driver_probe+0x1d/0xb0 [ 601.079000] [] efifb_init+0x273/0x292 [ 601.079000] [] do_one_initcall+0x102/0x1c0 [ 601.079000] [] kernel_init_freeable+0x15d/0x1ef [ 601.079000] [] kernel_init+0xe/0xf0 [ 601.079000] [] ret_from_fork+0x7c/0xb0 [ 601.079000] -> #0 (&fb_info->lock){+.+.+.}: [ 601.079000] [] __lock_acquire+0x1e18/0x1f10 [ 601.079000] [] lock_acquire+0xa1/0x140 [ 601.079000] [] mutex_lock_nested+0x7a/0x3b0 [ 601.079000] [] lock_fb_info+0x26/0x60 [ 601.079000] [] fbcon_blank+0x29b/0x2e0 [ 601.079000] [] do_blank_screen+0x1d8/0x280 [ 601.079000] [] console_callback+0x64/0x160 [ 601.079000] [] process_one_work+0x1f5/0x540 [ 601.079000] [] worker_thread+0x11c/0x370 [ 601.079000] [] kthread+0xed/0x100 [ 601.079000] [] ret_from_fork+0x7c/0xb0 [ 601.079000] other info that might help us debug this: [ 601.079000] Possible unsafe locking scenario: [ 601.079000] CPU0 CPU1 [ 601.079000] ---- ---- [ 601.079000] lock(console_lock); [ 601.079000] lock(&fb_info->lock); [ 601.079000] lock(console_lock); [ 601.079000] lock(&fb_info->lock); [ 601.079000] *** DEADLOCK *** so we reorder the lock sequence the same as it in console_callback() to avoid this issue. And following Tomi's suggestion, fix these similar issues all in fb subsystem. Signed-off-by: Gu Zheng Signed-off-by: Tomi Valkeinen --- drivers/video/sh_mobile_lcdcfb.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) (limited to 'drivers/video/sh_mobile_lcdcfb.c') diff --git a/drivers/video/sh_mobile_lcdcfb.c b/drivers/video/sh_mobile_lcdcfb.c index eaeae0fd0962..ab85ad6c25ec 100644 --- a/drivers/video/sh_mobile_lcdcfb.c +++ b/drivers/video/sh_mobile_lcdcfb.c @@ -574,8 +574,9 @@ static int sh_mobile_lcdc_display_notify(struct sh_mobile_lcdc_chan *ch, switch (event) { case SH_MOBILE_LCDC_EVENT_DISPLAY_CONNECT: /* HDMI plug in */ + console_lock(); if (lock_fb_info(info)) { - console_lock(); + ch->display.width = monspec->max_x * 10; ch->display.height = monspec->max_y * 10; @@ -594,19 +595,20 @@ static int sh_mobile_lcdc_display_notify(struct sh_mobile_lcdc_chan *ch, fb_set_suspend(info, 0); } - console_unlock(); + unlock_fb_info(info); } + console_unlock(); break; case SH_MOBILE_LCDC_EVENT_DISPLAY_DISCONNECT: /* HDMI disconnect */ + console_lock(); if (lock_fb_info(info)) { - console_lock(); fb_set_suspend(info, 1); - console_unlock(); unlock_fb_info(info); } + console_unlock(); break; case SH_MOBILE_LCDC_EVENT_DISPLAY_MODE: -- cgit v1.2.3