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Date: Tue, 2 Sep 2014 11:03:12 +0200 (CEST)
From: Jiri Kosina <jkosina@...e.cz>
To: Vincent Donnefort <vdonnefort@...il.com>,
Bryan Wu <cooloney@...il.com>,
Linus Torvalds <torvalds@...ux-foundation.org>
cc: Hugh Dickins <hughd@...gle.com>, Tejun Heo <tj@...nel.org>,
linux-kernel@...r.kernel.org
Subject: [PATCH] Revert "leds: convert blink timer to workqueue"
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.
[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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