The following commit has been merged into the sched/core branch of tip: Commit-ID: 8e12ab7c0e9f73ebfbcd6d37ece738f1825d58c8 Gitweb: https://git.kernel.org/tip/8e12ab7c0e9f73ebfbcd6d37ece738f1825d58c8 Author: Mark Rutland <mark.rutland@xxxxxxx> AuthorDate: Mon, 14 Feb 2022 16:52:15 Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx> CommitterDate: Sat, 19 Feb 2022 11:11:08 +01:00 arm64: entry: Centralize preemption decision For historical reasons, the decision of whether or not to preempt is spread across arm64_preempt_schedule_irq() and __el1_irq(), and it would be clearer if this were all in one place. Also, arm64_preempt_schedule_irq() calls lockdep_assert_irqs_disabled(), but this is redundant, as we have a subsequent identical assertion in __exit_to_kernel_mode(), and preempt_schedule_irq() will BUG_ON(!irqs_disabled()) anyway. This patch removes the redundant assertion and centralizes the preemption decision making within arm64_preempt_schedule_irq(). Other than the slight change to assertion behaviour, there should be no functional change as a result of this patch. Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Acked-by: Ard Biesheuvel <ardb@xxxxxxxxxx> Acked-by: Catalin Marinas <catalin.marinas@xxxxxxx> Acked-by: Frederic Weisbecker <frederic@xxxxxxxxxx> Link: https://lore.kernel.org/r/20220214165216.2231574-7-mark.rutland@xxxxxxx --- arch/arm64/kernel/entry-common.c | 20 +++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-) diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c index ef7fcef..2c639b6 100644 --- a/arch/arm64/kernel/entry-common.c +++ b/arch/arm64/kernel/entry-common.c @@ -222,7 +222,16 @@ static void noinstr arm64_exit_el1_dbg(struct pt_regs *regs) static void __sched arm64_preempt_schedule_irq(void) { - lockdep_assert_irqs_disabled(); + if (!IS_ENABLED(CONFIG_PREEMPTION)) + return; + + /* + * Note: thread_info::preempt_count includes both thread_info::count + * and thread_info::need_resched, and is not equivalent to + * preempt_count(). + */ + if (READ_ONCE(current_thread_info()->preempt_count) != 0) + return; /* * DAIF.DA are cleared at the start of IRQ/FIQ handling, and when GIC @@ -438,14 +447,7 @@ static __always_inline void __el1_irq(struct pt_regs *regs, do_interrupt_handler(regs, handler); irq_exit_rcu(); - /* - * Note: thread_info::preempt_count includes both thread_info::count - * and thread_info::need_resched, and is not equivalent to - * preempt_count(). - */ - if (IS_ENABLED(CONFIG_PREEMPTION) && - READ_ONCE(current_thread_info()->preempt_count) == 0) - arm64_preempt_schedule_irq(); + arm64_preempt_schedule_irq(); exit_to_kernel_mode(regs); }
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