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Message-ID: <CABcS5h0m10aWDuK5fK4C-mzMMwLyXJ_cehoTgWFutvPPrv30HQ@mail.gmail.com>
Date: Mon, 1 Aug 2011 09:42:43 +0100
From: Rolando Martins <rolando.martins@...il.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>,
LKML <linux-kernel@...r.kernel.org>,
linux-rt-users <linux-rt-users@...r.kernel.org>,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [ANNOUNCE] 3.0-rt6
Hi Peter,
is there any progress on the CONFIG_RT_GROUP_SCHED front?
I don't know if this is related, but in 33-rt if I used a low (=100)
cpu_runtime_us and cpu_period_us then I would get some freezes
(something that does not happen in 2.6.39).
Thanks,
Rolando
On Thu, Jul 28, 2011 at 10:43 PM, Thomas Gleixner <tglx@...utronix.de> wrote:
> Dear RT Folks,
>
> I'm pleased to announce the 3.0-rt6 release.
>
> Changes versus 3.0-rt4 (I pushed out a rt5 w/o announce)
>
> * pin_cpu fix (Yong Zhang)
>
> * Various compile fixes (Yong Zhang & myself)
>
> * Serial fix for omap
>
> * Clocksource lockless watchdog reset
>
> * Reenabled CONFIG_RCU_BOOST (problem is unreproducible and maybe
> related to NO_HZ, which is still disabled. Paul is working on it!)
>
> * KGDB work^Whackaround (Jason Wessel)
>
> The kgdb workaround is really a hack and wants to be replaced by a
> proper overhaul for the console/tty maze.
> See: kgb-serial-hackaround.patch
>
> As I said yesterday, I'm preparing for vanishing from the net.
>
> Please keep on testing and sending patches. Peter Zijlstra kindly
> volunteered to cover for me. He'll pick up stuff and eventually push
> out releases when a reasonable number of sane patches hits his inbox.
>
> If you reply to that mail, please keep the Cc list intact to make sure
> that all interested folks see it. It does not matter whether you are
> subscribed to a particular mailing list or not. Just keep your fingers
> away from the Cc list unless you have a very good reason to do
> so. Hint for GUI mail "client" users: Hit "Reply to all" ....
>
> For all those who are addicted to roadmaps, here is the roadmap I'm
> caring about for the next two weeks:
>
> http://maps.google.com/maps?q=Fuchsenloch,+Schlier&hl=en&z=16
>
> For the curious: Fuchsenloch == Fox hole. IOW: The place where fox and
> rabbit say Good Night to each other.
>
> And for those who care about estimates, here are my momentary
> favourite Dilberts on this topic:
>
> http://dilbert.com/strips/comic/1995-11-10/
> http://dilbert.com/strips/comic/2010-05-05/
>
> Patch against 3.0 can be found here:
>
> http://www.kernel.org/pub/linux/kernel/projects/rt/patch-3.0-rt6.patch.bz2
>
> The split quilt queue is available at:
>
> http://www.kernel.org/pub/linux/kernel/projects/rt/patches-3.0-rt6.tar.bz2
>
> Delta patch against 3.0-rt4 below.
>
> Thanks,
>
> tglx
> ----
> arch/arm/include/asm/mmu.h | 2 +-
> drivers/tty/serial/8250.c | 13 +++++++++----
> drivers/tty/serial/omap-serial.c | 8 +++-----
> include/linux/kdb.h | 2 ++
> init/Kconfig | 2 +-
> kernel/cpu.c | 4 +++-
> kernel/debug/kdb/kdb_io.c | 6 ++----
> kernel/hrtimer.c | 4 +---
> kernel/time/clocksource.c | 38 ++++++++++++++++++--------------------
> localversion-rt | 2 +-
> 10 files changed, 41 insertions(+), 40 deletions(-)
>
> Index: linux-2.6/arch/arm/include/asm/mmu.h
> ===================================================================
> --- linux-2.6.orig/arch/arm/include/asm/mmu.h
> +++ linux-2.6/arch/arm/include/asm/mmu.h
> @@ -16,7 +16,7 @@ typedef struct {
>
> /* init_mm.context.id_lock should be initialized. */
> #define INIT_MM_CONTEXT(name) \
> - .context.id_lock = __SPIN_LOCK_UNLOCKED(name.context.id_lock),
> + .context.id_lock = __RAW_SPIN_LOCK_UNLOCKED(name.context.id_lock),
> #else
> #define ASID(mm) (0)
> #endif
> Index: linux-2.6/drivers/tty/serial/8250.c
> ===================================================================
> --- linux-2.6.orig/drivers/tty/serial/8250.c
> +++ linux-2.6/drivers/tty/serial/8250.c
> @@ -38,6 +38,7 @@
> #include <linux/nmi.h>
> #include <linux/mutex.h>
> #include <linux/slab.h>
> +#include <linux/kdb.h>
>
> #include <asm/io.h>
> #include <asm/irq.h>
> @@ -2894,10 +2895,14 @@ serial8250_console_write(struct console
>
> touch_nmi_watchdog();
>
> - if (up->port.sysrq || oops_in_progress)
> - locked = spin_trylock_irqsave(&up->port.lock, flags);
> - else
> - spin_lock_irqsave(&up->port.lock, flags);
> + if (unlikely(in_kdb_printk())) {
> + locked = 0;
> + } else {
> + if (up->port.sysrq || oops_in_progress)
> + locked = spin_trylock_irqsave(&up->port.lock, flags);
> + else
> + spin_lock_irqsave(&up->port.lock, flags);
> + }
>
> /*
> * First save the IER then disable the interrupts
> Index: linux-2.6/init/Kconfig
> ===================================================================
> --- linux-2.6.orig/init/Kconfig
> +++ linux-2.6/init/Kconfig
> @@ -493,7 +493,7 @@ config TREE_RCU_TRACE
>
> config RCU_BOOST
> bool "Enable RCU priority boosting"
> - depends on RT_MUTEXES && PREEMPT_RCU && !RT_PREEMPT_FULL
> + depends on RT_MUTEXES && PREEMPT_RCU
> default n
> help
> This option boosts the priority of preempted RCU readers that
> Index: linux-2.6/kernel/cpu.c
> ===================================================================
> --- linux-2.6.orig/kernel/cpu.c
> +++ linux-2.6/kernel/cpu.c
> @@ -75,9 +75,11 @@ static DEFINE_PER_CPU(struct hotplug_pcp
> */
> void pin_current_cpu(void)
> {
> - struct hotplug_pcp *hp = &__get_cpu_var(hotplug_pcp);
> + struct hotplug_pcp *hp;
>
> retry:
> + hp = &__get_cpu_var(hotplug_pcp);
> +
> if (!hp->unplug || hp->refcount || preempt_count() > 1 ||
> hp->unplug == current || (current->flags & PF_STOMPER)) {
> hp->refcount++;
> Index: linux-2.6/kernel/hrtimer.c
> ===================================================================
> --- linux-2.6.orig/kernel/hrtimer.c
> +++ linux-2.6/kernel/hrtimer.c
> @@ -1294,11 +1294,9 @@ static void __run_hrtimer(struct hrtimer
> timer->state &= ~HRTIMER_STATE_CALLBACK;
> }
>
> -
> -#ifdef CONFIG_PREEMPT_RT_BASE
> -
> static enum hrtimer_restart hrtimer_wakeup(struct hrtimer *timer);
>
> +#ifdef CONFIG_PREEMPT_RT_BASE
> static void hrtimer_rt_reprogram(int restart, struct hrtimer *timer,
> struct hrtimer_clock_base *base)
> {
> Index: linux-2.6/localversion-rt
> ===================================================================
> --- linux-2.6.orig/localversion-rt
> +++ linux-2.6/localversion-rt
> @@ -1 +1 @@
> --rt4
> +-rt6
> Index: linux-2.6/kernel/time/clocksource.c
> ===================================================================
> --- linux-2.6.orig/kernel/time/clocksource.c
> +++ linux-2.6/kernel/time/clocksource.c
> @@ -186,6 +186,7 @@ static struct timer_list watchdog_timer;
> static DECLARE_WORK(watchdog_work, clocksource_watchdog_work);
> static DEFINE_SPINLOCK(watchdog_lock);
> static int watchdog_running;
> +static atomic_t watchdog_reset_pending;
>
> static int clocksource_watchdog_kthread(void *data);
> static void __clocksource_change_rating(struct clocksource *cs, int rating);
> @@ -247,12 +248,14 @@ static void clocksource_watchdog(unsigne
> struct clocksource *cs;
> cycle_t csnow, wdnow;
> int64_t wd_nsec, cs_nsec;
> - int next_cpu;
> + int next_cpu, reset_pending;
>
> spin_lock(&watchdog_lock);
> if (!watchdog_running)
> goto out;
>
> + reset_pending = atomic_read(&watchdog_reset_pending);
> +
> list_for_each_entry(cs, &watchdog_list, wd_list) {
>
> /* Clocksource already marked unstable? */
> @@ -268,7 +271,8 @@ static void clocksource_watchdog(unsigne
> local_irq_enable();
>
> /* Clocksource initialized ? */
> - if (!(cs->flags & CLOCK_SOURCE_WATCHDOG)) {
> + if (!(cs->flags & CLOCK_SOURCE_WATCHDOG) ||
> + atomic_read(&watchdog_reset_pending)) {
> cs->flags |= CLOCK_SOURCE_WATCHDOG;
> cs->wd_last = wdnow;
> cs->cs_last = csnow;
> @@ -283,8 +287,11 @@ static void clocksource_watchdog(unsigne
> cs->cs_last = csnow;
> cs->wd_last = wdnow;
>
> + if (atomic_read(&watchdog_reset_pending))
> + continue;
> +
> /* Check the deviation from the watchdog clocksource. */
> - if (abs(cs_nsec - wd_nsec) > WATCHDOG_THRESHOLD) {
> + if ((abs(cs_nsec - wd_nsec) > WATCHDOG_THRESHOLD)) {
> clocksource_unstable(cs, cs_nsec - wd_nsec);
> continue;
> }
> @@ -303,6 +310,13 @@ static void clocksource_watchdog(unsigne
> }
>
> /*
> + * We only clear the watchdog_reset_pending, when we did a
> + * full cycle through all clocksources.
> + */
> + if (reset_pending)
> + atomic_dec(&watchdog_reset_pending);
> +
> + /*
> * Cycle through CPUs to check if the CPUs stay synchronized
> * to each other.
> */
> @@ -344,23 +358,7 @@ static inline void clocksource_reset_wat
>
> static void clocksource_resume_watchdog(void)
> {
> - unsigned long flags;
> -
> - /*
> - * We use trylock here to avoid a potential dead lock when
> - * kgdb calls this code after the kernel has been stopped with
> - * watchdog_lock held. When watchdog_lock is held we just
> - * return and accept, that the watchdog might trigger and mark
> - * the monitored clock source (usually TSC) unstable.
> - *
> - * This does not affect the other caller clocksource_resume()
> - * because at this point the kernel is UP, interrupts are
> - * disabled and nothing can hold watchdog_lock.
> - */
> - if (!spin_trylock_irqsave(&watchdog_lock, flags))
> - return;
> - clocksource_reset_watchdog();
> - spin_unlock_irqrestore(&watchdog_lock, flags);
> + atomic_inc(&watchdog_reset_pending);
> }
>
> static void clocksource_enqueue_watchdog(struct clocksource *cs)
> Index: linux-2.6/drivers/tty/serial/omap-serial.c
> ===================================================================
> --- linux-2.6.orig/drivers/tty/serial/omap-serial.c
> +++ linux-2.6/drivers/tty/serial/omap-serial.c
> @@ -947,13 +947,12 @@ serial_omap_console_write(struct console
> unsigned int ier;
> int locked = 1;
>
> - local_irq_save(flags);
> if (up->port.sysrq)
> locked = 0;
> else if (oops_in_progress)
> - locked = spin_trylock(&up->port.lock);
> + locked = spin_trylock_irqsave(&up->port.lock, flags);
> else
> - spin_lock(&up->port.lock);
> + spin_lock_irqsave(&up->port.lock, flags);
>
> /*
> * First save the IER then disable the interrupts
> @@ -980,8 +979,7 @@ serial_omap_console_write(struct console
> check_modem_status(up);
>
> if (locked)
> - spin_unlock(&up->port.lock);
> - local_irq_restore(flags);
> + spin_unlock_irqrestore(&up->port.lock, flags);
> }
>
> static int __init
> Index: linux-2.6/include/linux/kdb.h
> ===================================================================
> --- linux-2.6.orig/include/linux/kdb.h
> +++ linux-2.6/include/linux/kdb.h
> @@ -153,12 +153,14 @@ extern int kdb_register(char *, kdb_func
> extern int kdb_register_repeat(char *, kdb_func_t, char *, char *,
> short, kdb_repeat_t);
> extern int kdb_unregister(char *);
> +#define in_kdb_printk() (kdb_trap_printk)
> #else /* ! CONFIG_KGDB_KDB */
> #define kdb_printf(...)
> #define kdb_init(x)
> #define kdb_register(...)
> #define kdb_register_repeat(...)
> #define kdb_uregister(x)
> +#define in_kdb_printk() (0)
> #endif /* CONFIG_KGDB_KDB */
> enum {
> KDB_NOT_INITIALIZED,
> Index: linux-2.6/kernel/debug/kdb/kdb_io.c
> ===================================================================
> --- linux-2.6.orig/kernel/debug/kdb/kdb_io.c
> +++ linux-2.6/kernel/debug/kdb/kdb_io.c
> @@ -539,7 +539,6 @@ int vkdb_printf(const char *fmt, va_list
> int diag;
> int linecount;
> int logging, saved_loglevel = 0;
> - int saved_trap_printk;
> int got_printf_lock = 0;
> int retlen = 0;
> int fnd, len;
> @@ -550,8 +549,6 @@ int vkdb_printf(const char *fmt, va_list
> unsigned long uninitialized_var(flags);
>
> preempt_disable();
> - saved_trap_printk = kdb_trap_printk;
> - kdb_trap_printk = 0;
>
> /* Serialize kdb_printf if multiple cpus try to write at once.
> * But if any cpu goes recursive in kdb, just print the output,
> @@ -807,7 +804,6 @@ kdb_print_out:
> } else {
> __release(kdb_printf_lock);
> }
> - kdb_trap_printk = saved_trap_printk;
> preempt_enable();
> return retlen;
> }
> @@ -817,9 +813,11 @@ int kdb_printf(const char *fmt, ...)
> va_list ap;
> int r;
>
> + kdb_trap_printk++;
> va_start(ap, fmt);
> r = vkdb_printf(fmt, ap);
> va_end(ap);
> + kdb_trap_printk--;
>
> return r;
> }
> --
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