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    Subject[GIT PULL] core/printk changes for v3.1
    Linus,

    Please pull the latest core-printk-for-linus git tree from:

    git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip.git core-printk-for-linus

    ( These are just the tested-safe commits - the ones that were causing
    problems are not included. )

    Thanks,

    Ingo

    ------------------>
    Peter Zijlstra (3):
    printk: Release console_sem after logbuf_lock
    printk: Fix console_sem vs logbuf_lock unlock race
    lockdep: Fix trace_[soft,hard]irqs_[on,off]() recursion


    kernel/lockdep.c | 30 ++++++++++++++++++++----------
    kernel/printk.c | 24 +++++++++++++++++++++---
    2 files changed, 41 insertions(+), 13 deletions(-)

    diff --git a/kernel/lockdep.c b/kernel/lockdep.c
    index 63437d0..81968a0 100644
    --- a/kernel/lockdep.c
    +++ b/kernel/lockdep.c
    @@ -2478,15 +2478,10 @@ mark_held_locks(struct task_struct *curr, enum mark_type mark)
    /*
    * Hardirqs will be enabled:
    */
    -void trace_hardirqs_on_caller(unsigned long ip)
    +static void __trace_hardirqs_on_caller(unsigned long ip)
    {
    struct task_struct *curr = current;

    - time_hardirqs_on(CALLER_ADDR0, ip);
    -
    - if (unlikely(!debug_locks || current->lockdep_recursion))
    - return;
    -
    if (DEBUG_LOCKS_WARN_ON(unlikely(early_boot_irqs_disabled)))
    return;

    @@ -2502,8 +2497,6 @@ void trace_hardirqs_on_caller(unsigned long ip)
    /* we'll do an OFF -> ON transition: */
    curr->hardirqs_enabled = 1;

    - if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
    - return;
    if (DEBUG_LOCKS_WARN_ON(current->hardirq_context))
    return;
    /*
    @@ -2525,6 +2518,21 @@ void trace_hardirqs_on_caller(unsigned long ip)
    curr->hardirq_enable_event = ++curr->irq_events;
    debug_atomic_inc(hardirqs_on_events);
    }
    +
    +void trace_hardirqs_on_caller(unsigned long ip)
    +{
    + time_hardirqs_on(CALLER_ADDR0, ip);
    +
    + if (unlikely(!debug_locks || current->lockdep_recursion))
    + return;
    +
    + if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
    + return;
    +
    + current->lockdep_recursion = 1;
    + __trace_hardirqs_on_caller(ip);
    + current->lockdep_recursion = 0;
    +}
    EXPORT_SYMBOL(trace_hardirqs_on_caller);

    void trace_hardirqs_on(void)
    @@ -2574,7 +2582,7 @@ void trace_softirqs_on(unsigned long ip)
    {
    struct task_struct *curr = current;

    - if (unlikely(!debug_locks))
    + if (unlikely(!debug_locks || current->lockdep_recursion))
    return;

    if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
    @@ -2585,6 +2593,7 @@ void trace_softirqs_on(unsigned long ip)
    return;
    }

    + current->lockdep_recursion = 1;
    /*
    * We'll do an OFF -> ON transition:
    */
    @@ -2599,6 +2608,7 @@ void trace_softirqs_on(unsigned long ip)
    */
    if (curr->hardirqs_enabled)
    mark_held_locks(curr, SOFTIRQ);
    + current->lockdep_recursion = 0;
    }

    /*
    @@ -2608,7 +2618,7 @@ void trace_softirqs_off(unsigned long ip)
    {
    struct task_struct *curr = current;

    - if (unlikely(!debug_locks))
    + if (unlikely(!debug_locks || current->lockdep_recursion))
    return;

    if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
    diff --git a/kernel/printk.c b/kernel/printk.c
    index 3518539..37dff34 100644
    --- a/kernel/printk.c
    +++ b/kernel/printk.c
    @@ -782,7 +782,7 @@ static inline int can_use_console(unsigned int cpu)
    static int console_trylock_for_printk(unsigned int cpu)
    __releases(&logbuf_lock)
    {
    - int retval = 0;
    + int retval = 0, wake = 0;

    if (console_trylock()) {
    retval = 1;
    @@ -795,12 +795,14 @@ static int console_trylock_for_printk(unsigned int cpu)
    */
    if (!can_use_console(cpu)) {
    console_locked = 0;
    - up(&console_sem);
    + wake = 1;
    retval = 0;
    }
    }
    printk_cpu = UINT_MAX;
    spin_unlock(&logbuf_lock);
    + if (wake)
    + up(&console_sem);
    return retval;
    }
    static const char recursion_bug_msg [] =
    @@ -1242,7 +1244,7 @@ void console_unlock(void)
    {
    unsigned long flags;
    unsigned _con_start, _log_end;
    - unsigned wake_klogd = 0;
    + unsigned wake_klogd = 0, retry = 0;

    if (console_suspended) {
    up(&console_sem);
    @@ -1251,6 +1253,7 @@ void console_unlock(void)

    console_may_schedule = 0;

    +again:
    for ( ; ; ) {
    spin_lock_irqsave(&logbuf_lock, flags);
    wake_klogd |= log_start - log_end;
    @@ -1271,8 +1274,23 @@ void console_unlock(void)
    if (unlikely(exclusive_console))
    exclusive_console = NULL;

    + spin_unlock(&logbuf_lock);
    +
    up(&console_sem);
    +
    + /*
    + * Someone could have filled up the buffer again, so re-check if there's
    + * something to flush. In case we cannot trylock the console_sem again,
    + * there's a new owner and the console_unlock() from them will do the
    + * flush, no worries.
    + */
    + spin_lock(&logbuf_lock);
    + if (con_start != log_end)
    + retry = 1;
    spin_unlock_irqrestore(&logbuf_lock, flags);
    + if (retry && console_trylock())
    + goto again;
    +
    if (wake_klogd)
    wake_up_klogd();
    }

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