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Message-ID: <20240222051253.1361002-1-jstultz@google.com>
Date: Wed, 21 Feb 2024 21:12:37 -0800
From: John Stultz <jstultz@...gle.com>
To: LKML <linux-kernel@...r.kernel.org>
Cc: John Stultz <jstultz@...gle.com>, Thomas Gleixner <tglx@...utronix.de>,
Frederic Weisbecker <frederic@...nel.org>, Steven Rostedt <rostedt@...dmis.org>, kernel-team@...roid.com
Subject: [RFC][PATCH] hrtimer: Use printk_deferred_once for hrtimer_interrupt message
With qemu, I constantly see lockdep warnings after the
hrimter_interrupt message is printed:
[ 43.434557] hrtimer: interrupt took 6517564 ns
[ 43.435000]
[ 43.435000] =============================
[ 43.435000] [ BUG: Invalid wait context ]
[ 43.435000] 6.8.0-rc5-00002-g28763ef29a5b #3743 Not tainted
[ 43.435000] -----------------------------
[ 43.435000] lock_torture_wr/605 is trying to lock:
[ 43.435000] ffffffffbdcdc6f8 (&port_lock_key){-...}-{3:3}, at: serial8250_console_write+0xdd/0x710
[ 43.435000] other info that might help us debug this:
[ 43.435000] context-{2:2}
[ 43.435000] 4 locks held by lock_torture_wr/605:
[ 43.435000] #0: ffffffffbd6f1de8 (torture_mutex_init#4){+.+.}-{4:4}, at: torture_mutex_nested_lock+0x4b/0x70
[ 43.435000] #1: ffffffffbb557260 (console_lock){+.+.}-{0:0}, at: vprintk_emit+0xd3/0x330
[ 43.435000] #2: ffffffffbb5572d0 (console_srcu){....}-{0:0}, at: console_flush_all+0xd6/0x6b0
[ 43.435000] #3: ffffffffbb396e20 (console_owner){-...}-{0:0}, at: console_flush_all+0x2a0/0x6b0
[ 43.435000] stack backtrace:
[ 43.435000] CPU: 36 PID: 605 Comm: lock_torture_wr Not tainted 6.8.0-rc5-00002-g28763ef29a5b #3743
[ 43.435000] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
[ 43.435000] Call Trace:
[ 43.435000] <IRQ>
[ 43.435000] dump_stack_lvl+0x57/0x90
[ 43.435000] __lock_acquire+0xd07/0x3260
[ 43.435000] ? __pfx___lock_acquire+0x10/0x10
[ 43.435000] ? memchr+0x1e/0x50
[ 43.435000] lock_acquire+0x159/0x3b0
[ 43.435000] ? serial8250_console_write+0xdd/0x710
[ 43.435000] ? __pfx_lock_acquire+0x10/0x10
[ 43.435000] ? __pfx___lock_acquire+0x10/0x10
[ 43.435000] _raw_spin_lock_irqsave+0x42/0x60
[ 43.435000] ? serial8250_console_write+0xdd/0x710
[ 43.435000] serial8250_console_write+0xdd/0x710
[ 43.435000] ? __pfx_serial8250_console_write+0x10/0x10
[ 43.435000] ? __pfx_lock_release+0x10/0x10
[ 43.435000] ? do_raw_spin_lock+0x104/0x180
[ 43.435000] ? __pfx_do_raw_spin_lock+0x10/0x10
[ 43.435000] ? console_flush_all+0x2a0/0x6b0
[ 43.435000] console_flush_all+0x2ea/0x6b0
[ 43.435000] ? console_flush_all+0x2a0/0x6b0
[ 43.435000] ? __pfx_console_flush_all+0x10/0x10
[ 43.435000] ? __pfx_lock_acquire+0x10/0x10
[ 43.435000] console_unlock+0x9d/0x150
[ 43.435000] ? __pfx_console_unlock+0x10/0x10
[ 43.435000] ? vprintk_emit+0xd3/0x330
[ 43.435000] ? __down_trylock_console_sem+0x62/0xa0
[ 43.435000] ? vprintk_emit+0xd3/0x330
[ 43.435000] vprintk_emit+0xdc/0x330
[ 43.435000] _printk+0x92/0xb0
[ 43.435000] ? __pfx__printk+0x10/0x10
[ 43.435000] ? hrtimer_interrupt+0x2f0/0x360
[ 43.439262] __sysvec_apic_timer_interrupt+0xb8/0x290
[ 43.439345] sysvec_apic_timer_interrupt+0x8a/0xb0
[ 43.439345] </IRQ>
[ 43.439345] <TASK>
[ 43.439345] asm_sysvec_apic_timer_interrupt+0x16/0x20
I thought the new printk work was going to resolve this, but
apparently not, so to avoid trying to printk in this problematic
context, lets use prink_deferred_once() instead.
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Frederic Weisbecker <frederic@...nel.org>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: kernel-team@...roid.com
Signed-off-by: John Stultz <jstultz@...gle.com>
---
kernel/time/hrtimer.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index edb0f821dcea..e6b060403384 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -1870,7 +1870,8 @@ void hrtimer_interrupt(struct clock_event_device *dev)
else
expires_next = ktime_add(now, delta);
tick_program_event(expires_next, 1);
- pr_warn_once("hrtimer: interrupt took %llu ns\n", ktime_to_ns(delta));
+ printk_deferred_once(KERN_WARNING "hrtimer: interrupt took %llu ns\n",
+ ktime_to_ns(delta));
}
/* called with interrupts disabled */
--
2.44.0.rc0.258.g7320e95886-goog
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