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Wysocki" , Arjan van de Ven , "Paul E . McKenney" , Frederic Weisbecker , Rik van Riel , Anna-Maria Behnsen Subject: [PATCH v5 11/18] timer: Split out "get next timer interrupt" functionality Date: Wed, 1 Mar 2023 15:17:37 +0100 Message-Id: <20230301141744.16063-12-anna-maria@linutronix.de> In-Reply-To: <20230301141744.16063-1-anna-maria@linutronix.de> References: <20230301141744.16063-1-anna-maria@linutronix.de> MIME-Version: 1.0 X-Spam-Status: No, score=-4.4 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED,SPF_HELO_NONE, SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1759175621166903850?= X-GMAIL-MSGID: =?utf-8?q?1759175621166903850?= The functionallity for getting the next timer interrupt in get_next_timer_interrupt() is splitted into a separate function fetch_next_timer_interrupt() to be usable by other callsides. This is preparatory work for the conversion of the NOHZ timer placement to a pull at expiry time model. No functional change. Signed-off-by: Anna-Maria Behnsen Reviewed-by: Frederic Weisbecker --- v5: Update commit message --- kernel/time/timer.c | 91 +++++++++++++++++++++++++-------------------- 1 file changed, 50 insertions(+), 41 deletions(-) diff --git a/kernel/time/timer.c b/kernel/time/timer.c index ff41d978cb22..dfc744545159 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -1944,6 +1944,46 @@ static unsigned long next_timer_interrupt(struct timer_base *base) return base->next_expiry; } +static unsigned long fetch_next_timer_interrupt(struct timer_base *base_local, + struct timer_base *base_global, + unsigned long basej, u64 basem, + struct timer_events *tevt) +{ + unsigned long nextevt_local, nextevt_global; + bool local_first; + + nextevt_local = next_timer_interrupt(base_local); + nextevt_global = next_timer_interrupt(base_global); + + /* + * Check whether the local event is expiring before or at the same + * time as the global event. + * + * Note, that nextevt_global and nextevt_local might be based on + * different base->clk values. So it's not guaranteed that + * comparing with empty bases results in a correct local_first. + */ + if (base_local->timers_pending && base_global->timers_pending) + local_first = time_before_eq(nextevt_local, nextevt_global); + else + local_first = base_local->timers_pending; + + /* + * Update tevt->* values: + * + * If the local queue expires first, then the global event can + * be ignored. If the global queue is empty, nothing to do + * either. + */ + if (!local_first && base_global->timers_pending) + tevt->global = basem + (u64)(nextevt_global - basej) * TICK_NSEC; + + if (base_local->timers_pending) + tevt->local = basem + (u64)(nextevt_local - basej) * TICK_NSEC; + + return local_first ? nextevt_local : nextevt_global; +} + /* * Forward base clock is done only when @basej is past base->clk, otherwise * base-clk might be rewind. @@ -1976,7 +2016,7 @@ u64 get_next_timer_interrupt(unsigned long basej, u64 basem) struct timer_events tevt = { .local = KTIME_MAX, .global = KTIME_MAX }; unsigned long nextevt, nextevt_local, nextevt_global; struct timer_base *base_local, *base_global; - bool local_first, is_idle; + bool is_idle; /* * Pretend that there is no timer pending if the cpu is offline. @@ -1991,8 +2031,11 @@ u64 get_next_timer_interrupt(unsigned long basej, u64 basem) raw_spin_lock(&base_local->lock); raw_spin_lock_nested(&base_global->lock, SINGLE_DEPTH_NESTING); - nextevt_local = next_timer_interrupt(base_local); - nextevt_global = next_timer_interrupt(base_global); + nextevt = fetch_next_timer_interrupt(base_local, base_global, + basej, basem, &tevt); + + nextevt_local = base_local->next_expiry; + nextevt_global = base_global->next_expiry; /* * We have a fresh next event. Check whether we can forward the @@ -2001,21 +2044,6 @@ u64 get_next_timer_interrupt(unsigned long basej, u64 basem) forward_base_clk(base_local, nextevt_local, basej); forward_base_clk(base_global, nextevt_global, basej); - /* - * Check whether the local event is expiring before or at the same - * time as the global event. - * - * Note, that nextevt_global and nextevt_local might be based on - * different base->clk values. So it's not guaranteed that - * comparing with empty bases results in a correct local_first. - */ - if (base_local->timers_pending && base_global->timers_pending) - local_first = time_before_eq(nextevt_local, nextevt_global); - else - local_first = base_local->timers_pending; - - nextevt = local_first ? nextevt_local : nextevt_global; - /* * Bases are idle if the next event is more than a tick away. Also * the tick is stopped so any added timer must forward the base clk @@ -2028,6 +2056,9 @@ u64 get_next_timer_interrupt(unsigned long basej, u64 basem) /* We need to mark both bases in sync */ base_local->is_idle = base_global->is_idle = is_idle; + raw_spin_unlock(&base_global->lock); + raw_spin_unlock(&base_local->lock); + /* * If the bases are not marked idle, i.e one of the events is at * max. one tick away, then the CPU can't go into a NOHZ idle @@ -2040,31 +2071,9 @@ u64 get_next_timer_interrupt(unsigned long basej, u64 basem) if (time_before(nextevt, basej)) nextevt = basej; tevt.local = basem + (u64)(nextevt - basej) * TICK_NSEC; - goto unlock; + tevt.global = KTIME_MAX; } - /* - * If the bases are marked idle, i.e. the next event on both the - * local and the global queue are farther away than a tick, - * evaluate both bases. No need to check whether one of the bases - * has an already expired timer as this is caught by the !is_idle - * condition above. - */ - if (base_local->timers_pending) - tevt.local = basem + (u64)(nextevt_local - basej) * TICK_NSEC; - - /* - * If the local queue expires first, then the global event can be - * ignored. The CPU wakes up before that. If the global queue is - * empty, nothing to do either. - */ - if (!local_first && base_global->timers_pending) - tevt.global = basem + (u64)(nextevt_global - basej) * TICK_NSEC; - -unlock: - raw_spin_unlock(&base_global->lock); - raw_spin_unlock(&base_local->lock); - tevt.local = min_t(u64, tevt.local, tevt.global); return cmp_next_hrtimer_event(basem, tevt.local);