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);
}
|