* [PATCH RT 1/4] net: sched: dev_deactivate_many(): use msleep(1) instead of yield() to wait for outstanding qdisc_run calls
2014-03-13 10:46 [PATCH RT 0/4] Linux 3.2.55-rt81-rc1 Steven Rostedt
@ 2014-03-13 10:46 ` Steven Rostedt
2014-03-13 10:46 ` [PATCH RT 2/4] fs: jbd2: pull your plug when waiting for space Steven Rostedt
` (2 subsequent siblings)
3 siblings, 0 replies; 6+ messages in thread
From: Steven Rostedt @ 2014-03-13 10:46 UTC (permalink / raw)
To: linux-kernel, linux-rt-users
Cc: Thomas Gleixner, Carsten Emde, Sebastian Andrzej Siewior,
John Kacur, Paul Gortmaker, stable-rt, Marc Kleine-Budde
[-- Attachment #1: 0001-net-sched-dev_deactivate_many-use-msleep-1-instead-o.patch --]
[-- Type: text/plain, Size: 3286 bytes --]
3.2.55-rt81-rc stable review patch.
If anyone has any objections, please let me know.
------------------
From: Marc Kleine-Budde <mkl@pengutronix.de>
On PREEMPT_RT enabled systems the interrupt handler run as threads at prio 50
(by default). If a high priority userspace process tries to shut down a busy
network interface it might spin in a yield loop waiting for the device to
become idle. With the interrupt thread having a lower priority than the
looping process it might never be scheduled and so result in a deadlock on UP
systems.
With Magic SysRq the following backtrace can be produced:
> test_app R running 0 174 168 0x00000000
> [<c02c7070>] (__schedule+0x220/0x3fc) from [<c02c7870>] (preempt_schedule_irq+0x48/0x80)
> [<c02c7870>] (preempt_schedule_irq+0x48/0x80) from [<c0008fa8>] (svc_preempt+0x8/0x20)
> [<c0008fa8>] (svc_preempt+0x8/0x20) from [<c001a984>] (local_bh_enable+0x18/0x88)
> [<c001a984>] (local_bh_enable+0x18/0x88) from [<c025316c>] (dev_deactivate_many+0x220/0x264)
> [<c025316c>] (dev_deactivate_many+0x220/0x264) from [<c023be04>] (__dev_close_many+0x64/0xd4)
> [<c023be04>] (__dev_close_many+0x64/0xd4) from [<c023be9c>] (__dev_close+0x28/0x3c)
> [<c023be9c>] (__dev_close+0x28/0x3c) from [<c023f7f0>] (__dev_change_flags+0x88/0x130)
> [<c023f7f0>] (__dev_change_flags+0x88/0x130) from [<c023f904>] (dev_change_flags+0x10/0x48)
> [<c023f904>] (dev_change_flags+0x10/0x48) from [<c024c140>] (do_setlink+0x370/0x7ec)
> [<c024c140>] (do_setlink+0x370/0x7ec) from [<c024d2f0>] (rtnl_newlink+0x2b4/0x450)
> [<c024d2f0>] (rtnl_newlink+0x2b4/0x450) from [<c024cfa0>] (rtnetlink_rcv_msg+0x158/0x1f4)
> [<c024cfa0>] (rtnetlink_rcv_msg+0x158/0x1f4) from [<c0256740>] (netlink_rcv_skb+0xac/0xc0)
> [<c0256740>] (netlink_rcv_skb+0xac/0xc0) from [<c024bbd8>] (rtnetlink_rcv+0x18/0x24)
> [<c024bbd8>] (rtnetlink_rcv+0x18/0x24) from [<c02561b8>] (netlink_unicast+0x13c/0x198)
> [<c02561b8>] (netlink_unicast+0x13c/0x198) from [<c025651c>] (netlink_sendmsg+0x264/0x2e0)
> [<c025651c>] (netlink_sendmsg+0x264/0x2e0) from [<c022af98>] (sock_sendmsg+0x78/0x98)
> [<c022af98>] (sock_sendmsg+0x78/0x98) from [<c022bb50>] (___sys_sendmsg.part.25+0x268/0x278)
> [<c022bb50>] (___sys_sendmsg.part.25+0x268/0x278) from [<c022cf08>] (__sys_sendmsg+0x48/0x78)
> [<c022cf08>] (__sys_sendmsg+0x48/0x78) from [<c0009320>] (ret_fast_syscall+0x0/0x2c)
This patch works around the problem by replacing yield() by msleep(1), giving
the interrupt thread time to finish, similar to other changes contained in the
rt patch set. Using wait_for_completion() instead would probably be a better
solution.
Cc: stable-rt@vger.kernel.org
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
net/sched/sch_generic.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 69fca27..9ede52e 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -847,7 +847,7 @@ void dev_deactivate_many(struct list_head *head)
/* Wait for outstanding qdisc_run calls. */
list_for_each_entry(dev, head, unreg_list)
while (some_qdisc_is_busy(dev))
- yield();
+ msleep(1);
}
void dev_deactivate(struct net_device *dev)
--
1.8.5.3
^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH RT 3/4] cpu_chill: Add a UNINTERRUPTIBLE hrtimer_nanosleep
2014-03-13 10:46 [PATCH RT 0/4] Linux 3.2.55-rt81-rc1 Steven Rostedt
2014-03-13 10:46 ` [PATCH RT 1/4] net: sched: dev_deactivate_many(): use msleep(1) instead of yield() to wait for outstanding qdisc_run calls Steven Rostedt
2014-03-13 10:46 ` [PATCH RT 2/4] fs: jbd2: pull your plug when waiting for space Steven Rostedt
@ 2014-03-13 10:46 ` Steven Rostedt
2014-03-13 10:46 ` [PATCH RT 4/4] Linux 3.2.55-rt81-rc Steven Rostedt
3 siblings, 0 replies; 6+ messages in thread
From: Steven Rostedt @ 2014-03-13 10:46 UTC (permalink / raw)
To: linux-kernel, linux-rt-users
Cc: Thomas Gleixner, Carsten Emde, Sebastian Andrzej Siewior,
John Kacur, Paul Gortmaker, stable-rt, Ulrich Obergfell
[-- Attachment #1: 0003-cpu_chill-Add-a-UNINTERRUPTIBLE-hrtimer_nanosleep.patch --]
[-- Type: text/plain, Size: 4135 bytes --]
3.2.55-rt81-rc stable review patch.
If anyone has any objections, please let me know.
------------------
From: Steven Rostedt <rostedt@goodmis.org>
We hit another bug that was caused by switching cpu_chill() from
msleep() to hrtimer_nanosleep().
This time it is a livelock. The problem is that hrtimer_nanosleep()
calls schedule with the state == TASK_INTERRUPTIBLE. But these means
that if a signal is pending, the scheduler wont schedule, and will
simply change the current task state back to TASK_RUNNING. This
nullifies the whole point of cpu_chill() in the first place. That is,
if a task is spinning on a try_lock() and it preempted the owner of the
lock, if it has a signal pending, it will never give up the CPU to let
the owner of the lock run.
I made a static function __hrtimer_nanosleep() that takes a fifth
parameter "state", which determines the task state of that the
nanosleep() will be in. The normal hrtimer_nanosleep() will act the
same, but cpu_chill() will call the __hrtimer_nanosleep() directly with
the TASK_UNINTERRUPTIBLE state.
cpu_chill() only cares that the first sleep happens, and does not care
about the state of the restart schedule (in hrtimer_nanosleep_restart).
Cc: stable-rt@vger.kernel.org
Reported-by: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
kernel/hrtimer.c | 25 ++++++++++++++++++-------
1 file changed, 18 insertions(+), 7 deletions(-)
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 71acc21..0316f75 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -1726,12 +1726,13 @@ void hrtimer_init_sleeper(struct hrtimer_sleeper *sl, struct task_struct *task)
}
EXPORT_SYMBOL_GPL(hrtimer_init_sleeper);
-static int __sched do_nanosleep(struct hrtimer_sleeper *t, enum hrtimer_mode mode)
+static int __sched do_nanosleep(struct hrtimer_sleeper *t, enum hrtimer_mode mode,
+ unsigned long state)
{
hrtimer_init_sleeper(t, current);
do {
- set_current_state(TASK_INTERRUPTIBLE);
+ set_current_state(state);
hrtimer_start_expires(&t->timer, mode);
if (!hrtimer_active(&t->timer))
t->task = NULL;
@@ -1775,7 +1776,8 @@ long __sched hrtimer_nanosleep_restart(struct restart_block *restart)
HRTIMER_MODE_ABS);
hrtimer_set_expires_tv64(&t.timer, restart->nanosleep.expires);
- if (do_nanosleep(&t, HRTIMER_MODE_ABS))
+ /* cpu_chill() does not care about restart state. */
+ if (do_nanosleep(&t, HRTIMER_MODE_ABS, TASK_INTERRUPTIBLE))
goto out;
rmtp = restart->nanosleep.rmtp;
@@ -1792,8 +1794,10 @@ out:
return ret;
}
-long hrtimer_nanosleep(struct timespec *rqtp, struct timespec __user *rmtp,
- const enum hrtimer_mode mode, const clockid_t clockid)
+static long
+__hrtimer_nanosleep(struct timespec *rqtp, struct timespec __user *rmtp,
+ const enum hrtimer_mode mode, const clockid_t clockid,
+ unsigned long state)
{
struct restart_block *restart;
struct hrtimer_sleeper t;
@@ -1806,7 +1810,7 @@ long hrtimer_nanosleep(struct timespec *rqtp, struct timespec __user *rmtp,
hrtimer_init_on_stack(&t.timer, clockid, mode);
hrtimer_set_expires_range_ns(&t.timer, timespec_to_ktime(*rqtp), slack);
- if (do_nanosleep(&t, mode))
+ if (do_nanosleep(&t, mode, state))
goto out;
/* Absolute timers do not update the rmtp value and restart: */
@@ -1833,6 +1837,12 @@ out:
return ret;
}
+long hrtimer_nanosleep(struct timespec *rqtp, struct timespec __user *rmtp,
+ const enum hrtimer_mode mode, const clockid_t clockid)
+{
+ return __hrtimer_nanosleep(rqtp, rmtp, mode, clockid, TASK_INTERRUPTIBLE);
+}
+
SYSCALL_DEFINE2(nanosleep, struct timespec __user *, rqtp,
struct timespec __user *, rmtp)
{
@@ -1859,7 +1869,8 @@ void cpu_chill(void)
unsigned int freeze_flag = current->flags & PF_NOFREEZE;
current->flags |= PF_NOFREEZE;
- hrtimer_nanosleep(&tu, NULL, HRTIMER_MODE_REL, CLOCK_MONOTONIC);
+ __hrtimer_nanosleep(&tu, NULL, HRTIMER_MODE_REL, CLOCK_MONOTONIC,
+ TASK_UNINTERRUPTIBLE);
if (!freeze_flag)
current->flags &= ~PF_NOFREEZE;
}
--
1.8.5.3
^ permalink raw reply related [flat|nested] 6+ messages in thread