Messages in this thread Patch in this message | | | From | Frederic Weisbecker <> | Subject | [PATCH 18/21] rcu/context-tracking: Remove unused and/or unecessary middle functions | Date | Thu, 19 May 2022 16:58:20 +0200 |
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Some eqs functions are now only used internally by context tracking, so their public declarations can be removed.
Also middle functions such as rcu_user_*() and rcu_idle_*() which now directly call to rcu_eqs_enter() and rcu_eqs_exit() can be wiped out as well.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Cc: Paul E. McKenney <paulmck@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com> Cc: Uladzislau Rezki <uladzislau.rezki@sony.com> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: Nicolas Saenz Julienne <nsaenz@kernel.org> Cc: Marcelo Tosatti <mtosatti@redhat.com> Cc: Xiongfeng Wang <wangxiongfeng2@huawei.com> Cc: Yu Liao<liaoyu15@huawei.com> Cc: Phil Auld <pauld@redhat.com> Cc: Paul Gortmaker<paul.gortmaker@windriver.com> Cc: Alex Belits <abelits@marvell.com> --- Documentation/RCU/stallwarn.rst | 2 +- include/linux/hardirq.h | 8 --- include/linux/rcupdate.h | 8 --- include/linux/rcutiny.h | 2 - include/linux/rcutree.h | 2 - kernel/context_tracking.c | 95 +++++++++------------------------ 6 files changed, 25 insertions(+), 92 deletions(-)
diff --git a/Documentation/RCU/stallwarn.rst b/Documentation/RCU/stallwarn.rst index ce1f58a9d954..e38c587067fc 100644 --- a/Documentation/RCU/stallwarn.rst +++ b/Documentation/RCU/stallwarn.rst @@ -97,7 +97,7 @@ warnings: which will include additional debugging information. - A low-level kernel issue that either fails to invoke one of the - variants of rcu_user_enter(), rcu_user_exit(), ct_idle_enter(), + variants of rcu_eqs_enter(true), rcu_eqs_exit(true), ct_idle_enter(), ct_idle_exit(), ct_irq_enter(), or ct_irq_exit() on the one hand, or that invokes one of them too many times on the other. Historically, the most frequent issue has been an omission diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h index 345cdbe9c1b7..d57cab4d4c06 100644 --- a/include/linux/hardirq.h +++ b/include/linux/hardirq.h @@ -92,14 +92,6 @@ void irq_exit_rcu(void); #define arch_nmi_exit() do { } while (0) #endif -#ifdef CONFIG_TINY_RCU -static inline void rcu_nmi_enter(void) { } -static inline void rcu_nmi_exit(void) { } -#else -extern void rcu_nmi_enter(void); -extern void rcu_nmi_exit(void); -#endif - /* * NMI vs Tracing * -------------- diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index abbcd3dfcf06..c4489d79a0e9 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -105,14 +105,6 @@ static inline void rcu_sysrq_start(void) { } static inline void rcu_sysrq_end(void) { } #endif /* #else #ifdef CONFIG_RCU_STALL_COMMON */ -#ifdef CONFIG_NO_HZ_FULL -void rcu_user_enter(void); -void rcu_user_exit(void); -#else -static inline void rcu_user_enter(void) { } -static inline void rcu_user_exit(void) { } -#endif /* CONFIG_NO_HZ_FULL */ - #if defined(CONFIG_NO_HZ_FULL) && (!defined(CONFIG_GENERIC_ENTRY) || !defined(CONFIG_KVM_XFER_TO_GUEST_WORK)) void rcu_irq_work_resched(void); #else diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h index 5921d9ae7ab5..430aac8a7344 100644 --- a/include/linux/rcutiny.h +++ b/include/linux/rcutiny.h @@ -86,8 +86,6 @@ static inline int rcu_needs_cpu(void) static inline void rcu_virt_note_context_switch(int cpu) { } static inline void rcu_cpu_stall_reset(void) { } static inline int rcu_jiffies_till_stall_check(void) { return 21 * HZ; } -static inline void rcu_idle_enter(void) { } -static inline void rcu_idle_exit(void) { } static inline void rcu_irq_exit_check_preempt(void) { } #define rcu_is_idle_cpu(cpu) \ (is_idle_task(current) && !in_nmi() && !in_hardirq() && !in_serving_softirq()) diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index c31e4e526643..47eaa4cb0df7 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -47,8 +47,6 @@ unsigned long start_poll_synchronize_rcu(void); bool poll_state_synchronize_rcu(unsigned long oldstate); void cond_synchronize_rcu(unsigned long oldstate); -void rcu_idle_enter(void); -void rcu_idle_exit(void); bool rcu_is_idle_cpu(int cpu); #ifdef CONFIG_PROVE_RCU diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c index 4a1d33105f92..6152313ea787 100644 --- a/kernel/context_tracking.c +++ b/kernel/context_tracking.c @@ -189,17 +189,17 @@ static void noinstr rcu_eqs_exit(bool user) } /** - * rcu_nmi_exit - inform RCU of exit from NMI context + * ct_nmi_exit - inform RCU of exit from NMI context * * If we are returning from the outermost NMI handler that interrupted an * RCU-idle period, update ct->dynticks and ct->dynticks_nmi_nesting * to let the RCU grace-period handling know that the CPU is back to * being RCU-idle. * - * If you add or remove a call to rcu_nmi_exit(), be sure to test + * If you add or remove a call to ct_nmi_exit(), be sure to test * with CONFIG_RCU_EQS_DEBUG=y. */ -void noinstr rcu_nmi_exit(void) +void noinstr ct_nmi_exit(void) { struct context_tracking *ct = this_cpu_ptr(&context_tracking); @@ -242,7 +242,7 @@ void noinstr rcu_nmi_exit(void) } /** - * rcu_nmi_enter - inform RCU of entry to NMI context + * ct_nmi_enter - inform RCU of entry to NMI context * * If the CPU was idle from RCU's viewpoint, update ct->dynticks and * ct->dynticks_nmi_nesting to let the RCU grace-period handling know @@ -250,10 +250,10 @@ void noinstr rcu_nmi_exit(void) * long as the nesting level does not overflow an int. (You will probably * run out of stack space first.) * - * If you add or remove a call to rcu_nmi_enter(), be sure to test + * If you add or remove a call to ct_nmi_enter(), be sure to test * with CONFIG_RCU_EQS_DEBUG=y. */ -void noinstr rcu_nmi_enter(void) +void noinstr ct_nmi_enter(void) { long incby = 2; struct context_tracking *ct = this_cpu_ptr(&context_tracking); @@ -302,32 +302,33 @@ void noinstr rcu_nmi_enter(void) } /** - * rcu_idle_enter - inform RCU that current CPU is entering idle + * ct_idle_enter - inform RCU that current CPU is entering idle * * Enter idle mode, in other words, -leave- the mode in which RCU * read-side critical sections can occur. (Though RCU read-side * critical sections can occur in irq handlers in idle, a possibility * handled by irq_enter() and irq_exit().) * - * If you add or remove a call to rcu_idle_enter(), be sure to test with + * If you add or remove a call to ct_idle_enter(), be sure to test with * CONFIG_RCU_EQS_DEBUG=y. */ -void noinstr rcu_idle_enter(void) +void noinstr ct_idle_enter(void) { WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !raw_irqs_disabled()); rcu_eqs_enter(false); } +EXPORT_SYMBOL_GPL(ct_idle_enter); /** - * rcu_idle_exit - inform RCU that current CPU is leaving idle + * ct_idle_exit - inform RCU that current CPU is leaving idle * * Exit idle mode, in other words, -enter- the mode in which RCU * read-side critical sections can occur. * - * If you add or remove a call to rcu_idle_exit(), be sure to test with + * If you add or remove a call to ct_idle_exit(), be sure to test with * CONFIG_RCU_EQS_DEBUG=y. */ -void noinstr rcu_idle_exit(void) +void noinstr ct_idle_exit(void) { unsigned long flags; @@ -335,18 +336,6 @@ void noinstr rcu_idle_exit(void) rcu_eqs_exit(false); raw_local_irq_restore(flags); } -EXPORT_SYMBOL_GPL(rcu_idle_exit); - -noinstr void ct_idle_enter(void) -{ - rcu_idle_enter(); -} -EXPORT_SYMBOL_GPL(ct_idle_enter); - -void ct_idle_exit(void) -{ - rcu_idle_exit(); -} EXPORT_SYMBOL_GPL(ct_idle_exit); /** @@ -431,50 +420,8 @@ void noinstr ct_irq_exit_irqson(void) ct_irq_exit(); raw_local_irq_restore(flags); } - -noinstr void ct_nmi_enter(void) -{ - rcu_nmi_enter(); -} - -noinstr void ct_nmi_exit(void) -{ - rcu_nmi_exit(); -} #endif /* #ifdef CONFIG_CONTEXT_TRACKING_IDLE */ -#ifdef CONFIG_NO_HZ_FULL -/** - * rcu_user_enter - inform RCU that we are resuming userspace. - * - * Enter RCU idle mode right before resuming userspace. No use of RCU - * is permitted between this call and rcu_user_exit(). This way the - * CPU doesn't need to maintain the tick for RCU maintenance purposes - * when the CPU runs in userspace. - * - * If you add or remove a call to rcu_user_enter(), be sure to test with - * CONFIG_RCU_EQS_DEBUG=y. - */ -noinstr void rcu_user_enter(void) -{ - rcu_eqs_enter(true); -} - -/** - * rcu_user_exit - inform RCU that we are exiting userspace. - * - * Exit RCU idle mode while entering the kernel because it can - * run a RCU read side critical section anytime. - * - * If you add or remove a call to rcu_user_exit(), be sure to test with - * CONFIG_RCU_EQS_DEBUG=y. - */ -void noinstr rcu_user_exit(void) -{ - rcu_eqs_exit(true); -} -#endif /* #ifdef CONFIG_NO_HZ_FULL */ - #ifdef CONFIG_CONTEXT_TRACKING_USER #define CREATE_TRACE_POINTS @@ -542,7 +489,13 @@ void noinstr __ct_user_enter(enum ctx_state state) * that will fire and reschedule once we resume in user/guest mode. */ rcu_irq_work_resched(); - rcu_user_enter(); + /* + * Enter RCU idle mode right before resuming userspace. No use of RCU + * is permitted between this call and rcu_eqs_exit(). This way the + * CPU doesn't need to maintain the tick for RCU maintenance purposes + * when the CPU runs in userspace. + */ + rcu_eqs_enter(true); } /* * Even if context tracking is disabled on this CPU, because it's outside @@ -575,7 +528,7 @@ void ct_user_enter(enum ctx_state state) /* * Some contexts may involve an exception occuring in an irq, * leading to that nesting: - * ct_irq_enter() rcu_user_exit() rcu_user_exit() ct_irq_exit() + * ct_irq_enter() rcu_eqs_exit(true) rcu_eqs_enter(true) ct_irq_exit() * This would mess up the dyntick_nesting count though. And rcu_irq_*() * helpers are enough to protect RCU uses inside the exception. So * just return immediately if we detect we are in an IRQ. @@ -624,10 +577,10 @@ void noinstr __ct_user_exit(enum ctx_state state) if (__this_cpu_read(context_tracking.state) == state) { if (__this_cpu_read(context_tracking.active)) { /* - * We are going to run code that may use RCU. Inform - * RCU core about that (ie: we may need the tick again). + * Exit RCU idle mode while entering the kernel because it can + * run a RCU read side critical section anytime. */ - rcu_user_exit(); + rcu_eqs_exit(true); if (state == CONTEXT_USER) { instrumentation_begin(); vtime_user_exit(current); -- 2.25.1
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