80 lines
3.3 KiB
Diff
80 lines
3.3 KiB
Diff
|
From: John Ogness <john.ogness@linutronix.de>
|
||
|
|
Date: Wed, 4 Sep 2024 14:11:21 +0206
|
||
|
|
Subject: [PATCH 39/54] printk: Fail pr_flush() if before SYSTEM_SCHEDULING
|
||
|
|
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.11/older/patches-6.11-rt7.tar.xz
|
||
|
|
|
||
|
|
A follow-up change adds pr_flush() to console unregistration.
|
||
|
|
However, with boot consoles unregistration can happen very
|
||
|
|
early if there are also regular consoles registering as well.
|
||
|
|
In this case the pr_flush() is not important because all
|
||
|
|
consoles are flushed when checking the initial console sequence
|
||
|
|
number.
|
||
|
|
|
||
|
|
Allow pr_flush() to fail if @system_state has not yet reached
|
||
|
|
SYSTEM_SCHEDULING. This avoids might_sleep() and msleep()
|
||
|
|
explosions that would otherwise occur:
|
||
|
|
|
||
|
|
[ 0.436739][ T0] printk: legacy console [ttyS0] enabled
|
||
|
|
[ 0.439820][ T0] printk: legacy bootconsole [earlyser0] disabled
|
||
|
|
[ 0.446822][ T0] BUG: scheduling while atomic: swapper/0/0/0x00000002
|
||
|
|
[ 0.450491][ T0] 1 lock held by swapper/0/0:
|
||
|
|
[ 0.457897][ T0] #0: ffffffff82ae5f88 (console_mutex){+.+.}-{4:4}, at: console_list_lock+0x20/0x70
|
||
|
|
[ 0.463141][ T0] Modules linked in:
|
||
|
|
[ 0.465307][ T0] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.10.0-rc1+ #372
|
||
|
|
[ 0.469394][ T0] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014
|
||
|
|
[ 0.474402][ T0] Call Trace:
|
||
|
|
[ 0.476246][ T0] <TASK>
|
||
|
|
[ 0.481473][ T0] dump_stack_lvl+0x93/0xb0
|
||
|
|
[ 0.483949][ T0] dump_stack+0x10/0x20
|
||
|
|
[ 0.486256][ T0] __schedule_bug+0x68/0x90
|
||
|
|
[ 0.488753][ T0] __schedule+0xb9b/0xd80
|
||
|
|
[ 0.491179][ T0] ? lock_release+0xb5/0x270
|
||
|
|
[ 0.493732][ T0] schedule+0x43/0x170
|
||
|
|
[ 0.495998][ T0] schedule_timeout+0xc5/0x1e0
|
||
|
|
[ 0.498634][ T0] ? __pfx_process_timeout+0x10/0x10
|
||
|
|
[ 0.501522][ T0] ? msleep+0x13/0x50
|
||
|
|
[ 0.503728][ T0] msleep+0x3c/0x50
|
||
|
|
[ 0.505847][ T0] __pr_flush.constprop.0.isra.0+0x56/0x500
|
||
|
|
[ 0.509050][ T0] ? _printk+0x58/0x80
|
||
|
|
[ 0.511332][ T0] ? lock_is_held_type+0x9c/0x110
|
||
|
|
[ 0.514106][ T0] unregister_console_locked+0xe1/0x450
|
||
|
|
[ 0.517144][ T0] register_console+0x509/0x620
|
||
|
|
[ 0.519827][ T0] ? __pfx_univ8250_console_init+0x10/0x10
|
||
|
|
[ 0.523042][ T0] univ8250_console_init+0x24/0x40
|
||
|
|
[ 0.525845][ T0] console_init+0x43/0x210
|
||
|
|
[ 0.528280][ T0] start_kernel+0x493/0x980
|
||
|
|
[ 0.530773][ T0] x86_64_start_reservations+0x18/0x30
|
||
|
|
[ 0.533755][ T0] x86_64_start_kernel+0xae/0xc0
|
||
|
|
[ 0.536473][ T0] common_startup_64+0x12c/0x138
|
||
|
|
[ 0.539210][ T0] </TASK>
|
||
|
|
|
||
|
|
And then the kernel goes into an infinite loop complaining about:
|
||
|
|
|
||
|
|
1. releasing a pinned lock
|
||
|
|
2. unpinning an unpinned lock
|
||
|
|
3. bad: scheduling from the idle thread!
|
||
|
|
4. goto 1
|
||
|
|
|
||
|
|
Signed-off-by: John Ogness <john.ogness@linutronix.de>
|
||
|
|
Reviewed-by: Petr Mladek <pmladek@suse.com>
|
||
|
|
Link: https://lore.kernel.org/r/20240904120536.115780-3-john.ogness@linutronix.de
|
||
|
|
Signed-off-by: Petr Mladek <pmladek@suse.com>
|
||
|
|
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
|
||
|
|
---
|
||
|
|
kernel/printk/printk.c | 4 ++++
|
||
|
|
1 file changed, 4 insertions(+)
|
||
|
|
|
||
|
|
--- a/kernel/printk/printk.c
|
||
|
|
+++ b/kernel/printk/printk.c
|
||
|
|
@@ -3992,6 +3992,10 @@ static bool __pr_flush(struct console *c
|
||
|
|
u64 diff;
|
||
|
|
u64 seq;
|
||
|
|
|
||
|
|
+ /* Sorry, pr_flush() will not work this early. */
|
||
|
|
+ if (system_state < SYSTEM_SCHEDULING)
|
||
|
|
+ return false;
|
||
|
|
+
|
||
|
|
might_sleep();
|
||
|
|
|
||
|
|
seq = prb_next_reserve_seq(prb);
|