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Date: Tue, 2 Sep 2014 10:02:26 -0700
From: Bryan Wu <cooloney@...il.com>
To: Jiri Kosina <jkosina@...e.cz>
Cc: Vincent Donnefort <vdonnefort@...il.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Hugh Dickins <hughd@...gle.com>, Tejun Heo <tj@...nel.org>,
lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Revert "leds: convert blink timer to workqueue"
On Tue, Sep 2, 2014 at 2:03 AM, Jiri Kosina <jkosina@...e.cz> wrote:
> This reverts commit 8b37e1bef5a6b60e949e28a4db3006e4b00bd758.
>
> It's broken as it changes led_blink_set() in a way that it can now sleep
> (while synchronously waiting for workqueue to be cancelled). That's a
> problem, because it's possible that this function gets called from atomic
> context (tpt_trig_timer() takes a readlock and thus disables preemption).
>
> This has been brought up 3 weeks ago already [1] but no proper fix has
> materialized, and I keep seeing the problem since 3.18-rc1.
>
Is this 3.18-rc1? I think it should be 3.17-rc1, right?
-Bryan
> [1] https://lkml.org/lkml/2014/8/16/128
>
> BUG: sleeping function called from invalid context at kernel/workqueue.c:2650
> in_atomic(): 1, irqs_disabled(): 0, pid: 2335, name: wpa_supplicant
> 5 locks held by wpa_supplicant/2335:
> #0: (rtnl_mutex){+.+.+.}, at: [<ffffffff814c7c92>] rtnl_lock+0x12/0x20
> #1: (&wdev->mtx){+.+.+.}, at: [<ffffffffc06e649c>] cfg80211_mgd_wext_siwessid+0x5c/0x180 [cfg80211]
> #2: (&local->mtx){+.+.+.}, at: [<ffffffffc0817dea>] ieee80211_prep_connection+0x17a/0x9a0 [mac80211]
> #3: (&local->chanctx_mtx){+.+.+.}, at: [<ffffffffc08081ed>] ieee80211_vif_use_channel+0x5d/0x2a0 [mac80211]
> #4: (&trig->leddev_list_lock){.+.+..}, at: [<ffffffffc081e68c>] tpt_trig_timer+0xec/0x170 [mac80211]
> CPU: 0 PID: 2335 Comm: wpa_supplicant Not tainted 3.17.0-rc3 #1
> Hardware name: LENOVO 7470BN2/7470BN2, BIOS 6DET38WW (2.02 ) 12/19/2008
> ffff8800360b5a50 ffff8800751f76d8 ffffffff8159e97f ffff8800360b5a30
> ffff8800751f76e8 ffffffff810739a5 ffff8800751f77b0 ffffffff8106862f
> ffffffff810685d0 0aa2209200000000 ffff880000000004 ffff8800361c59d0
> Call Trace:
> [<ffffffff8159e97f>] dump_stack+0x4d/0x66
> [<ffffffff810739a5>] __might_sleep+0xe5/0x120
> [<ffffffff8106862f>] flush_work+0x5f/0x270
> [<ffffffff810685d0>] ? mod_delayed_work_on+0x80/0x80
> [<ffffffff810945ca>] ? mark_held_locks+0x6a/0x90
> [<ffffffff81068a5f>] ? __cancel_work_timer+0x6f/0x100
> [<ffffffff810946ed>] ? trace_hardirqs_on_caller+0xfd/0x1c0
> [<ffffffff81068a6b>] __cancel_work_timer+0x7b/0x100
> [<ffffffff81068b0e>] cancel_delayed_work_sync+0xe/0x10
> [<ffffffff8147cf3b>] led_blink_set+0x1b/0x40
> [<ffffffffc081e6b0>] tpt_trig_timer+0x110/0x170 [mac80211]
> [<ffffffffc081ecdd>] ieee80211_mod_tpt_led_trig+0x9d/0x160 [mac80211]
> [<ffffffffc07e4278>] __ieee80211_recalc_idle+0x98/0x140 [mac80211]
> [<ffffffffc07e59ce>] ieee80211_idle_off+0xe/0x10 [mac80211]
> [<ffffffffc0804e5b>] ieee80211_add_chanctx+0x3b/0x220 [mac80211]
> [<ffffffffc08062e4>] ieee80211_new_chanctx+0x44/0xf0 [mac80211]
> [<ffffffffc080838a>] ieee80211_vif_use_channel+0x1fa/0x2a0 [mac80211]
> [<ffffffffc0817df8>] ieee80211_prep_connection+0x188/0x9a0 [mac80211]
> [<ffffffffc081c246>] ieee80211_mgd_auth+0x256/0x2e0 [mac80211]
> [<ffffffffc07eab33>] ieee80211_auth+0x13/0x20 [mac80211]
> [<ffffffffc06cb006>] cfg80211_mlme_auth+0x106/0x270 [cfg80211]
> [<ffffffffc06ce085>] cfg80211_conn_do_work+0x155/0x3b0 [cfg80211]
> [<ffffffffc06cf670>] cfg80211_connect+0x3f0/0x540 [cfg80211]
> [<ffffffffc06e6148>] cfg80211_mgd_wext_connect+0x158/0x1f0 [cfg80211]
> [<ffffffffc06e651e>] cfg80211_mgd_wext_siwessid+0xde/0x180 [cfg80211]
> [<ffffffffc06e36c0>] ? cfg80211_wext_giwessid+0x50/0x50 [cfg80211]
> [<ffffffffc06e36dd>] cfg80211_wext_siwessid+0x1d/0x40 [cfg80211]
> [<ffffffff81584d0c>] ioctl_standard_iw_point+0x14c/0x3e0
> [<ffffffff810946ed>] ? trace_hardirqs_on_caller+0xfd/0x1c0
> [<ffffffff8158502a>] ioctl_standard_call+0x8a/0xd0
> [<ffffffff81584fa0>] ? ioctl_standard_iw_point+0x3e0/0x3e0
> [<ffffffff81584b76>] wireless_process_ioctl.constprop.10+0xb6/0x100
> [<ffffffff8158521d>] wext_handle_ioctl+0x5d/0xb0
> [<ffffffff814cfb29>] dev_ioctl+0x329/0x620
> [<ffffffff810946ed>] ? trace_hardirqs_on_caller+0xfd/0x1c0
> [<ffffffff8149c7f2>] sock_ioctl+0x142/0x2e0
> [<ffffffff811b0140>] do_vfs_ioctl+0x300/0x520
> [<ffffffff815a67fb>] ? sysret_check+0x1b/0x56
> [<ffffffff810946ed>] ? trace_hardirqs_on_caller+0xfd/0x1c0
> [<ffffffff811b03e1>] SyS_ioctl+0x81/0xa0
> [<ffffffff815a67d6>] system_call_fastpath+0x1a/0x1f
> wlan0: send auth to 00:0b:6b:3c:8c:e4 (try 1/3)
> wlan0: authenticated
> wlan0: associate with 00:0b:6b:3c:8c:e4 (try 1/3)
> wlan0: RX AssocResp from 00:0b:6b:3c:8c:e4 (capab=0x431 status=0 aid=2)
> wlan0: associated
> IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
> cfg80211: Calling CRDA for country: NA
> wlan0: Limiting TX power to 27 (27 - 0) dBm as advertised by 00:0b:6b:3c:8c:e4
>
> =================================
> [ INFO: inconsistent lock state ]
> 3.17.0-rc3 #1 Not tainted
> ---------------------------------
> inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
> swapper/0/0 [HC0[0]:SC1[1]:HE1:SE0] takes:
> ((&(&led_cdev->blink_work)->work)){+.?...}, at: [<ffffffff810685d0>] flush_work+0x0/0x270
> {SOFTIRQ-ON-W} state was registered at:
> [<ffffffff81094dbe>] __lock_acquire+0x30e/0x1a30
> [<ffffffff81096c81>] lock_acquire+0x91/0x110
> [<ffffffff81068608>] flush_work+0x38/0x270
> [<ffffffff81068a6b>] __cancel_work_timer+0x7b/0x100
> [<ffffffff81068b0e>] cancel_delayed_work_sync+0xe/0x10
> [<ffffffff8147cf3b>] led_blink_set+0x1b/0x40
> [<ffffffffc081e6b0>] tpt_trig_timer+0x110/0x170 [mac80211]
> [<ffffffffc081ecdd>] ieee80211_mod_tpt_led_trig+0x9d/0x160 [mac80211]
> [<ffffffffc07e4278>] __ieee80211_recalc_idle+0x98/0x140 [mac80211]
> [<ffffffffc07e59ce>] ieee80211_idle_off+0xe/0x10 [mac80211]
> [<ffffffffc0804e5b>] ieee80211_add_chanctx+0x3b/0x220 [mac80211]
> [<ffffffffc08062e4>] ieee80211_new_chanctx+0x44/0xf0 [mac80211]
> [<ffffffffc080838a>] ieee80211_vif_use_channel+0x1fa/0x2a0 [mac80211]
> [<ffffffffc0817df8>] ieee80211_prep_connection+0x188/0x9a0 [mac80211]
> [<ffffffffc081c246>] ieee80211_mgd_auth+0x256/0x2e0 [mac80211]
> [<ffffffffc07eab33>] ieee80211_auth+0x13/0x20 [mac80211]
> [<ffffffffc06cb006>] cfg80211_mlme_auth+0x106/0x270 [cfg80211]
> [<ffffffffc06ce085>] cfg80211_conn_do_work+0x155/0x3b0 [cfg80211]
> [<ffffffffc06cf670>] cfg80211_connect+0x3f0/0x540 [cfg80211]
> [<ffffffffc06e6148>] cfg80211_mgd_wext_connect+0x158/0x1f0 [cfg80211]
> [<ffffffffc06e651e>] cfg80211_mgd_wext_siwessid+0xde/0x180 [cfg80211]
> [<ffffffffc06e36dd>] cfg80211_wext_siwessid+0x1d/0x40 [cfg80211]
> [<ffffffff81584d0c>] ioctl_standard_iw_point+0x14c/0x3e0
> [<ffffffff8158502a>] ioctl_standard_call+0x8a/0xd0
> [<ffffffff81584b76>] wireless_process_ioctl.constprop.10+0xb6/0x100
> [<ffffffff8158521d>] wext_handle_ioctl+0x5d/0xb0
> [<ffffffff814cfb29>] dev_ioctl+0x329/0x620
> [<ffffffff8149c7f2>] sock_ioctl+0x142/0x2e0
> [<ffffffff811b0140>] do_vfs_ioctl+0x300/0x520
> [<ffffffff811b03e1>] SyS_ioctl+0x81/0xa0
> [<ffffffff815a67d6>] system_call_fastpath+0x1a/0x1f
> irq event stamp: 493416
> hardirqs last enabled at (493416): [<ffffffff81068a5f>] __cancel_work_timer+0x6f/0x100
> hardirqs last disabled at (493415): [<ffffffff81067e9f>] try_to_grab_pending+0x1f/0x160
> softirqs last enabled at (493408): [<ffffffff81053ced>] _local_bh_enable+0x1d/0x50
> softirqs last disabled at (493409): [<ffffffff81054c75>] irq_exit+0xa5/0xb0
>
> other info that might help us debug this:
> Possible unsafe locking scenario:
>
> CPU0
> ----
> lock((&(&led_cdev->blink_work)->work));
> <Interrupt>
> lock((&(&led_cdev->blink_work)->work));
>
> *** DEADLOCK ***
>
> 2 locks held by swapper/0/0:
> #0: (((&tpt_trig->timer))){+.-...}, at: [<ffffffff810b4c50>] call_timer_fn+0x0/0x180
> #1: (&trig->leddev_list_lock){.+.?..}, at: [<ffffffffc081e68c>] tpt_trig_timer+0xec/0x170 [mac80211]
>
> stack backtrace:
> CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.17.0-rc3 #1
> Hardware name: LENOVO 7470BN2/7470BN2, BIOS 6DET38WW (2.02 ) 12/19/2008
> ffffffff8246eb30 ffff88007c203b00 ffffffff8159e97f ffffffff81a194c0
> ffff88007c203b50 ffffffff81599c29 0000000000000001 ffffffff00000001
> ffff880000000000 0000000000000006 ffffffff81a194c0 ffffffff81093ad0
> Call Trace:
> <IRQ> [<ffffffff8159e97f>] dump_stack+0x4d/0x66
> [<ffffffff81599c29>] print_usage_bug+0x1f4/0x205
> [<ffffffff81093ad0>] ? check_usage_backwards+0x140/0x140
> [<ffffffff810944d3>] mark_lock+0x223/0x2b0
> [<ffffffff81094d60>] __lock_acquire+0x2b0/0x1a30
> [<ffffffff81096c81>] lock_acquire+0x91/0x110
> [<ffffffff810685d0>] ? mod_delayed_work_on+0x80/0x80
> [<ffffffffc081e5a0>] ? __ieee80211_get_rx_led_name+0x10/0x10 [mac80211]
> [<ffffffff81068608>] flush_work+0x38/0x270
> [<ffffffff810685d0>] ? mod_delayed_work_on+0x80/0x80
> [<ffffffff810945ca>] ? mark_held_locks+0x6a/0x90
> [<ffffffff81068a5f>] ? __cancel_work_timer+0x6f/0x100
> [<ffffffffc081e5a0>] ? __ieee80211_get_rx_led_name+0x10/0x10 [mac80211]
> [<ffffffff8109469d>] ? trace_hardirqs_on_caller+0xad/0x1c0
> [<ffffffffc081e5a0>] ? __ieee80211_get_rx_led_name+0x10/0x10 [mac80211]
> [<ffffffff81068a6b>] __cancel_work_timer+0x7b/0x100
> [<ffffffff81068b0e>] cancel_delayed_work_sync+0xe/0x10
> [<ffffffff8147cf3b>] led_blink_set+0x1b/0x40
> [<ffffffffc081e6b0>] tpt_trig_timer+0x110/0x170 [mac80211]
> [<ffffffff810b4cc5>] call_timer_fn+0x75/0x180
> [<ffffffff810b4c50>] ? process_timeout+0x10/0x10
> [<ffffffffc081e5a0>] ? __ieee80211_get_rx_led_name+0x10/0x10 [mac80211]
> [<ffffffff810b50ac>] run_timer_softirq+0x1fc/0x2f0
> [<ffffffff81054805>] __do_softirq+0x115/0x2e0
> [<ffffffff81054c75>] irq_exit+0xa5/0xb0
> [<ffffffff810049b3>] do_IRQ+0x53/0xf0
> [<ffffffff815a74af>] common_interrupt+0x6f/0x6f
> <EOI> [<ffffffff8147b56e>] ? cpuidle_enter_state+0x6e/0x180
> [<ffffffff8147b732>] cpuidle_enter+0x12/0x20
> [<ffffffff8108bba0>] cpu_startup_entry+0x330/0x360
> [<ffffffff8158fb51>] rest_init+0xc1/0xd0
> [<ffffffff8158fa90>] ? csum_partial_copy_generic+0x170/0x170
> [<ffffffff81af3ff2>] start_kernel+0x44f/0x45a
> [<ffffffff81af399c>] ? set_init_arg+0x53/0x53
> [<ffffffff81af35ad>] x86_64_start_reservations+0x2a/0x2c
> [<ffffffff81af36a0>] x86_64_start_kernel+0xf1/0xf4
>
> Cc: Vincent Donnefort <vdonnefort@...il.com>
> Cc: Bryan Wu <cooloney@...il.com>
> Cc: Hugh Dickins <hughd@...gle.com>
> Cc: Tejun Heo <tj@...nel.org>
> Signed-off-by: Jiri Kosina <jkosina@...e.cz>
> ---
> drivers/leds/led-class.c | 14 +++++++-------
> drivers/leds/led-core.c | 11 +++++------
> include/linux/leds.h | 3 ++-
> 3 files changed, 14 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
> index 129729d..aa29198 100644
> --- a/drivers/leds/led-class.c
> +++ b/drivers/leds/led-class.c
> @@ -15,10 +15,10 @@
> #include <linux/list.h>
> #include <linux/spinlock.h>
> #include <linux/device.h>
> +#include <linux/timer.h>
> #include <linux/err.h>
> #include <linux/ctype.h>
> #include <linux/leds.h>
> -#include <linux/workqueue.h>
> #include "leds.h"
>
> static struct class *leds_class;
> @@ -97,10 +97,9 @@ static const struct attribute_group *led_groups[] = {
> NULL,
> };
>
> -static void led_work_function(struct work_struct *ws)
> +static void led_timer_function(unsigned long data)
> {
> - struct led_classdev *led_cdev =
> - container_of(ws, struct led_classdev, blink_work.work);
> + struct led_classdev *led_cdev = (void *)data;
> unsigned long brightness;
> unsigned long delay;
>
> @@ -144,8 +143,7 @@ static void led_work_function(struct work_struct *ws)
> }
> }
>
> - queue_delayed_work(system_wq, &led_cdev->blink_work,
> - msecs_to_jiffies(delay));
> + mod_timer(&led_cdev->blink_timer, jiffies + msecs_to_jiffies(delay));
> }
>
> static void set_brightness_delayed(struct work_struct *ws)
> @@ -233,7 +231,9 @@ int led_classdev_register(struct device *parent, struct led_classdev *led_cdev)
>
> INIT_WORK(&led_cdev->set_brightness_work, set_brightness_delayed);
>
> - INIT_DELAYED_WORK(&led_cdev->blink_work, led_work_function);
> + init_timer(&led_cdev->blink_timer);
> + led_cdev->blink_timer.function = led_timer_function;
> + led_cdev->blink_timer.data = (unsigned long)led_cdev;
>
> #ifdef CONFIG_LEDS_TRIGGERS
> led_trigger_set_default(led_cdev);
> diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
> index 4bb1168..71b40d3 100644
> --- a/drivers/leds/led-core.c
> +++ b/drivers/leds/led-core.c
> @@ -16,7 +16,6 @@
> #include <linux/module.h>
> #include <linux/rwsem.h>
> #include <linux/leds.h>
> -#include <linux/workqueue.h>
> #include "leds.h"
>
> DECLARE_RWSEM(leds_list_lock);
> @@ -52,7 +51,7 @@ static void led_set_software_blink(struct led_classdev *led_cdev,
> return;
> }
>
> - queue_delayed_work(system_wq, &led_cdev->blink_work, 1);
> + mod_timer(&led_cdev->blink_timer, jiffies + 1);
> }
>
>
> @@ -76,7 +75,7 @@ void led_blink_set(struct led_classdev *led_cdev,
> unsigned long *delay_on,
> unsigned long *delay_off)
> {
> - cancel_delayed_work_sync(&led_cdev->blink_work);
> + del_timer_sync(&led_cdev->blink_timer);
>
> led_cdev->flags &= ~LED_BLINK_ONESHOT;
> led_cdev->flags &= ~LED_BLINK_ONESHOT_STOP;
> @@ -91,7 +90,7 @@ void led_blink_set_oneshot(struct led_classdev *led_cdev,
> int invert)
> {
> if ((led_cdev->flags & LED_BLINK_ONESHOT) &&
> - delayed_work_pending(&led_cdev->blink_work))
> + timer_pending(&led_cdev->blink_timer))
> return;
>
> led_cdev->flags |= LED_BLINK_ONESHOT;
> @@ -108,7 +107,7 @@ EXPORT_SYMBOL(led_blink_set_oneshot);
>
> void led_stop_software_blink(struct led_classdev *led_cdev)
> {
> - cancel_delayed_work_sync(&led_cdev->blink_work);
> + del_timer_sync(&led_cdev->blink_timer);
> led_cdev->blink_delay_on = 0;
> led_cdev->blink_delay_off = 0;
> }
> @@ -117,7 +116,7 @@ EXPORT_SYMBOL_GPL(led_stop_software_blink);
> void led_set_brightness(struct led_classdev *led_cdev,
> enum led_brightness brightness)
> {
> - /* delay brightness setting if need to stop soft-blink work */
> + /* delay brightness setting if need to stop soft-blink timer */
> if (led_cdev->blink_delay_on || led_cdev->blink_delay_off) {
> led_cdev->delayed_set_value = brightness;
> schedule_work(&led_cdev->set_brightness_work);
> diff --git a/include/linux/leds.h b/include/linux/leds.h
> index 6a599dc..e436864 100644
> --- a/include/linux/leds.h
> +++ b/include/linux/leds.h
> @@ -15,6 +15,7 @@
> #include <linux/list.h>
> #include <linux/spinlock.h>
> #include <linux/rwsem.h>
> +#include <linux/timer.h>
> #include <linux/workqueue.h>
>
> struct device;
> @@ -68,7 +69,7 @@ struct led_classdev {
> const char *default_trigger; /* Trigger to use */
>
> unsigned long blink_delay_on, blink_delay_off;
> - struct delayed_work blink_work;
> + struct timer_list blink_timer;
> int blink_brightness;
>
> struct work_struct set_brightness_work;
> --
> Jiri Kosina
> SUSE Labs
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