113 lines
4.2 KiB
Diff
113 lines
4.2 KiB
Diff
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From 2c91f2661cb66544c8c8e41721eb48788dfcec52 Mon Sep 17 00:00:00 2001
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From: Steven Rostedt <rostedt@goodmis.org>
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Date: Tue, 4 Mar 2014 12:28:32 -0500
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Subject: [PATCH 216/365] cpu_chill: Add a UNINTERRUPTIBLE hrtimer_nanosleep
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We hit another bug that was caused by switching cpu_chill() from
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msleep() to hrtimer_nanosleep().
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This time it is a livelock. The problem is that hrtimer_nanosleep()
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calls schedule with the state == TASK_INTERRUPTIBLE. But these means
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that if a signal is pending, the scheduler wont schedule, and will
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simply change the current task state back to TASK_RUNNING. This
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nullifies the whole point of cpu_chill() in the first place. That is,
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if a task is spinning on a try_lock() and it preempted the owner of the
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lock, if it has a signal pending, it will never give up the CPU to let
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the owner of the lock run.
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I made a static function __hrtimer_nanosleep() that takes a fifth
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parameter "state", which determines the task state of that the
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nanosleep() will be in. The normal hrtimer_nanosleep() will act the
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same, but cpu_chill() will call the __hrtimer_nanosleep() directly with
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the TASK_UNINTERRUPTIBLE state.
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cpu_chill() only cares that the first sleep happens, and does not care
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about the state of the restart schedule (in hrtimer_nanosleep_restart).
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Reported-by: Ulrich Obergfell <uobergfe@redhat.com>
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Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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kernel/time/hrtimer.c | 25 ++++++++++++++++++-------
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1 file changed, 18 insertions(+), 7 deletions(-)
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diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
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index a652e5bcbc37..d2fb17faae9f 100644
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--- a/kernel/time/hrtimer.c
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+++ b/kernel/time/hrtimer.c
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@@ -1669,12 +1669,13 @@ void hrtimer_init_sleeper(struct hrtimer_sleeper *sl, struct task_struct *task)
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}
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EXPORT_SYMBOL_GPL(hrtimer_init_sleeper);
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-static int __sched do_nanosleep(struct hrtimer_sleeper *t, enum hrtimer_mode mode)
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+static int __sched do_nanosleep(struct hrtimer_sleeper *t, enum hrtimer_mode mode,
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+ unsigned long state)
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{
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hrtimer_init_sleeper(t, current);
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do {
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- set_current_state(TASK_INTERRUPTIBLE);
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+ set_current_state(state);
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hrtimer_start_expires(&t->timer, mode);
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if (likely(t->task))
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@@ -1716,7 +1717,8 @@ long __sched hrtimer_nanosleep_restart(struct restart_block *restart)
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HRTIMER_MODE_ABS);
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hrtimer_set_expires_tv64(&t.timer, restart->nanosleep.expires);
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- if (do_nanosleep(&t, HRTIMER_MODE_ABS))
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+ /* cpu_chill() does not care about restart state. */
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+ if (do_nanosleep(&t, HRTIMER_MODE_ABS, TASK_INTERRUPTIBLE))
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goto out;
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rmtp = restart->nanosleep.rmtp;
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@@ -1733,8 +1735,10 @@ long __sched hrtimer_nanosleep_restart(struct restart_block *restart)
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return ret;
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}
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-long hrtimer_nanosleep(struct timespec *rqtp, struct timespec __user *rmtp,
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- const enum hrtimer_mode mode, const clockid_t clockid)
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+static long
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+__hrtimer_nanosleep(struct timespec *rqtp, struct timespec __user *rmtp,
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+ const enum hrtimer_mode mode, const clockid_t clockid,
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+ unsigned long state)
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{
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struct restart_block *restart;
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struct hrtimer_sleeper t;
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@@ -1747,7 +1751,7 @@ long hrtimer_nanosleep(struct timespec *rqtp, struct timespec __user *rmtp,
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hrtimer_init_on_stack(&t.timer, clockid, mode);
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hrtimer_set_expires_range_ns(&t.timer, timespec_to_ktime(*rqtp), slack);
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- if (do_nanosleep(&t, mode))
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+ if (do_nanosleep(&t, mode, state))
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goto out;
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/* Absolute timers do not update the rmtp value and restart: */
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@@ -1774,6 +1778,12 @@ long hrtimer_nanosleep(struct timespec *rqtp, struct timespec __user *rmtp,
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return ret;
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}
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+long hrtimer_nanosleep(struct timespec *rqtp, struct timespec __user *rmtp,
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+ const enum hrtimer_mode mode, const clockid_t clockid)
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+{
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+ return __hrtimer_nanosleep(rqtp, rmtp, mode, clockid, TASK_INTERRUPTIBLE);
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+}
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+
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SYSCALL_DEFINE2(nanosleep, struct timespec __user *, rqtp,
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struct timespec __user *, rmtp)
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{
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@@ -1800,7 +1810,8 @@ void cpu_chill(void)
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unsigned int freeze_flag = current->flags & PF_NOFREEZE;
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current->flags |= PF_NOFREEZE;
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- hrtimer_nanosleep(&tu, NULL, HRTIMER_MODE_REL, CLOCK_MONOTONIC);
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+ __hrtimer_nanosleep(&tu, NULL, HRTIMER_MODE_REL, CLOCK_MONOTONIC,
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+ TASK_UNINTERRUPTIBLE);
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if (!freeze_flag)
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current->flags &= ~PF_NOFREEZE;
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}
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--
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2.28.0
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