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    Subject[PATCH tip/core/rcu 07/10] rcu: Remove "cpu" argument to rcu_needs_cpu()
    Date
    From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>

    The "cpu" argument to rcu_needs_cpu() is always the current CPU, so drop
    it. This in turn allows the "cpu" argument to rcu_cpu_has_callbacks()
    to be removed, which allows the uses of "cpu" in both functions to be
    replaced with a this_cpu_ptr(). Again, the anticipated cross-CPU uses
    of these functions has been replaced by NO_HZ_FULL.

    Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    ---
    include/linux/rcupdate.h | 2 +-
    include/linux/rcutree.h | 2 +-
    kernel/rcu/tree.c | 4 ++--
    kernel/rcu/tree_plugin.h | 12 ++++++------
    kernel/time/tick-sched.c | 2 +-
    5 files changed, 11 insertions(+), 11 deletions(-)

    diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
    index b4ad275d90d0..4eb810832b19 100644
    --- a/include/linux/rcupdate.h
    +++ b/include/linux/rcupdate.h
    @@ -1103,7 +1103,7 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
    __kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head))

    #if defined(CONFIG_TINY_RCU) || defined(CONFIG_RCU_NOCB_CPU_ALL)
    -static inline int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies)
    +static inline int rcu_needs_cpu(unsigned long *delta_jiffies)
    {
    *delta_jiffies = ULONG_MAX;
    return 0;
    diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
    index 7b5484db1857..52953790dcca 100644
    --- a/include/linux/rcutree.h
    +++ b/include/linux/rcutree.h
    @@ -32,7 +32,7 @@

    void rcu_note_context_switch(void);
    #ifndef CONFIG_RCU_NOCB_CPU_ALL
    -int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies);
    +int rcu_needs_cpu(unsigned long *delta_jiffies);
    #endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */
    void rcu_cpu_stall_reset(void);

    diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
    index b591f1459240..d678a98caf1d 100644
    --- a/kernel/rcu/tree.c
    +++ b/kernel/rcu/tree.c
    @@ -3159,7 +3159,7 @@ static int rcu_pending(void)
    * non-NULL, store an indication of whether all callbacks are lazy.
    * (If there are no callbacks, all of them are deemed to be lazy.)
    */
    -static int __maybe_unused rcu_cpu_has_callbacks(int cpu, bool *all_lazy)
    +static int __maybe_unused rcu_cpu_has_callbacks(bool *all_lazy)
    {
    bool al = true;
    bool hc = false;
    @@ -3167,7 +3167,7 @@ static int __maybe_unused rcu_cpu_has_callbacks(int cpu, bool *all_lazy)
    struct rcu_state *rsp;

    for_each_rcu_flavor(rsp) {
    - rdp = per_cpu_ptr(rsp->rda, cpu);
    + rdp = this_cpu_ptr(rsp->rda);
    if (!rdp->nxtlist)
    continue;
    hc = true;
    diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
    index 495d4cce47a7..1797b76cb3ff 100644
    --- a/kernel/rcu/tree_plugin.h
    +++ b/kernel/rcu/tree_plugin.h
    @@ -1512,10 +1512,10 @@ static void rcu_prepare_kthreads(int cpu)
    * any flavor of RCU.
    */
    #ifndef CONFIG_RCU_NOCB_CPU_ALL
    -int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies)
    +int rcu_needs_cpu(unsigned long *delta_jiffies)
    {
    *delta_jiffies = ULONG_MAX;
    - return rcu_cpu_has_callbacks(cpu, NULL);
    + return rcu_cpu_has_callbacks(NULL);
    }
    #endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */

    @@ -1624,15 +1624,15 @@ static bool __maybe_unused rcu_try_advance_all_cbs(void)
    * The caller must have disabled interrupts.
    */
    #ifndef CONFIG_RCU_NOCB_CPU_ALL
    -int rcu_needs_cpu(int cpu, unsigned long *dj)
    +int rcu_needs_cpu(unsigned long *dj)
    {
    - struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
    + struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);

    /* Snapshot to detect later posting of non-lazy callback. */
    rdtp->nonlazy_posted_snap = rdtp->nonlazy_posted;

    /* If no callbacks, RCU doesn't need the CPU. */
    - if (!rcu_cpu_has_callbacks(cpu, &rdtp->all_lazy)) {
    + if (!rcu_cpu_has_callbacks(&rdtp->all_lazy)) {
    *dj = ULONG_MAX;
    return 0;
    }
    @@ -1679,7 +1679,7 @@ static void rcu_prepare_for_idle(int cpu)
    /* Handle nohz enablement switches conservatively. */
    tne = ACCESS_ONCE(tick_nohz_active);
    if (tne != rdtp->tick_nohz_enabled_snap) {
    - if (rcu_cpu_has_callbacks(cpu, NULL))
    + if (rcu_cpu_has_callbacks(NULL))
    invoke_rcu_core(); /* force nohz to see update. */
    rdtp->tick_nohz_enabled_snap = tne;
    return;
    diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
    index 7b5741fc4110..1f4356037a7d 100644
    --- a/kernel/time/tick-sched.c
    +++ b/kernel/time/tick-sched.c
    @@ -585,7 +585,7 @@ static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts,
    last_jiffies = jiffies;
    } while (read_seqretry(&jiffies_lock, seq));

    - if (rcu_needs_cpu(cpu, &rcu_delta_jiffies) ||
    + if (rcu_needs_cpu(&rcu_delta_jiffies) ||
    arch_needs_cpu() || irq_work_needs_cpu()) {
    next_jiffies = last_jiffies + 1;
    delta_jiffies = 1;
    --
    1.8.1.5


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