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    Subject[PATCH 25/32] softirq: Prepare for mixing all/per-vector masking
    Date
    In order to be able to mix and nest full and per vector softirq masking,
    we need to be able to track the nesting state using a "full masking"
    counter and a mask of "individual disabled vectors".

    Start with introducing the full masking counter. For now it's a simple
    mirror of softirq_count() because there is no per vector masking API
    yet.

    When this full masking counter is non 0, all softirq vectors are
    explicitly disabled.

    Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
    Cc: Mauro Carvalho Chehab <mchehab@s-opensource.com>
    Cc: Joel Fernandes <joel@joelfernandes.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Pavan Kondeti <pkondeti@codeaurora.org>
    Cc: Paul E . McKenney <paulmck@linux.vnet.ibm.com>
    Cc: David S . Miller <davem@davemloft.net>
    Cc: Ingo Molnar <mingo@kernel.org>
    Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    ---
    kernel/softirq.c | 33 ++++++++++++++++++++++-----------
    1 file changed, 22 insertions(+), 11 deletions(-)

    diff --git a/kernel/softirq.c b/kernel/softirq.c
    index 91dee716e139..4477a03afd94 100644
    --- a/kernel/softirq.c
    +++ b/kernel/softirq.c
    @@ -57,6 +57,12 @@ static struct softirq_action softirq_vec[NR_SOFTIRQS] __cacheline_aligned_in_smp

    DEFINE_PER_CPU(struct task_struct *, ksoftirqd);

    +struct softirq_nesting {
    + unsigned int disabled_all;
    +};
    +
    +static DEFINE_PER_CPU(struct softirq_nesting, softirq_nesting);
    +
    const char * const softirq_to_name[NR_SOFTIRQS] = {
    "HI", "TIMER", "NET_TX", "NET_RX", "BLOCK", "IRQ_POLL",
    "TASKLET", "SCHED", "HRTIMER", "RCU"
    @@ -118,11 +124,11 @@ void __local_bh_disable_ip(unsigned long ip, unsigned int cnt)
    * call the trace_preempt_off later.
    */
    __preempt_count_add(cnt);
    - /*
    - * Were softirqs turned off above:
    - */
    - if (softirq_count() == (cnt & SOFTIRQ_MASK))
    +
    + if (__this_cpu_inc_return(softirq_nesting.disabled_all) == 1) {
    + softirq_enabled_clear_mask(SOFTIRQ_ALL_MASK);
    trace_softirqs_off(ip);
    + }

    #ifdef CONFIG_TRACE_IRQFLAGS
    raw_local_irq_restore(flags);
    @@ -137,6 +143,15 @@ void __local_bh_disable_ip(unsigned long ip, unsigned int cnt)
    }
    EXPORT_SYMBOL(__local_bh_disable_ip);

    +static void local_bh_enable_common(unsigned long ip, unsigned int cnt)
    +{
    + if (__this_cpu_dec_return(softirq_nesting.disabled_all))
    + return;
    +
    + softirq_enabled_set(SOFTIRQ_ALL_MASK);
    + trace_softirqs_on(ip);
    +}
    +
    static void __local_bh_enable_no_softirq(unsigned int cnt)
    {
    lockdep_assert_irqs_disabled();
    @@ -144,8 +159,7 @@ static void __local_bh_enable_no_softirq(unsigned int cnt)
    if (preempt_count() == cnt)
    trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip());

    - if (softirq_count() == (cnt & SOFTIRQ_MASK))
    - trace_softirqs_on(_RET_IP_);
    + local_bh_enable_common(_RET_IP_, cnt);

    __preempt_count_sub(cnt);
    }
    @@ -168,11 +182,8 @@ void __local_bh_enable_ip(unsigned long ip, unsigned int cnt)
    #ifdef CONFIG_TRACE_IRQFLAGS
    local_irq_disable();
    #endif
    - /*
    - * Are softirqs going to be turned on now:
    - */
    - if (softirq_count() == SOFTIRQ_DISABLE_OFFSET)
    - trace_softirqs_on(ip);
    + local_bh_enable_common(ip, cnt);
    +
    /*
    * Keep preemption disabled until we are done with
    * softirq processing:
    --
    2.17.1
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