linux-kernel - [PATCH v2 1/2] time/sched_clock: Disable interrupts in sched_clock

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Message-Id: <20200107010630.954648-1-paul@crapouillou.net>
Date:   Tue,  7 Jan 2020 02:06:29 +0100
From:   Paul Cercueil <paul@...pouillou.net>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     od@...c.me, linux-kernel@...r.kernel.org,
        Paul Cercueil <paul@...pouillou.net>
Subject: [PATCH v2 1/2] time/sched_clock: Disable interrupts in sched_clock_register

Instead of issueing a warning if sched_clock_register is called from a
context where IRQs are enabled, the code now ensures that IRQs are
indeed disabled.

Signed-off-by: Paul Cercueil <paul@...pouillou.net>
---

Notes:
    v2: New patch

 kernel/time/sched_clock.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/kernel/time/sched_clock.c b/kernel/time/sched_clock.c
index dbd69052eaa6..e4332e3e2d56 100644
--- a/kernel/time/sched_clock.c
+++ b/kernel/time/sched_clock.c
@@ -169,14 +169,15 @@ sched_clock_register(u64 (*read)(void), int bits, unsigned long rate)
 {
 	u64 res, wrap, new_mask, new_epoch, cyc, ns;
 	u32 new_mult, new_shift;
-	unsigned long r;
+	unsigned long r, flags;
 	char r_unit;
 	struct clock_read_data rd;
 
 	if (cd.rate > rate)
 		return;
 
-	WARN_ON(!irqs_disabled());
+	/* Cannot register a sched_clock with interrupts on */
+	local_irq_save(flags);
 
 	/* Calculate the mult/shift to convert counter ticks to ns. */
 	clocks_calc_mult_shift(&new_mult, &new_shift, rate, NSEC_PER_SEC, 3600);
@@ -233,6 +234,8 @@ sched_clock_register(u64 (*read)(void), int bits, unsigned long rate)
 	if (irqtime > 0 || (irqtime == -1 && rate >= 1000000))
 		enable_sched_clock_irqtime();
 
+	local_irq_restore(flags);
+
 	pr_debug("Registered %pS as sched_clock source\n", read);
 }
 
-- 
2.24.1