While testing hotplug I got this BUG:
=============================
[ BUG: Invalid wait context ]
5.9.0-rc5+ #3 Not tainted
-----------------------------
migration/2/20 is trying to lock:
ffffffffb4315778 (&port->lock){-.-.}-{3:3}, at:
serial8250_console_write+0x8e/0x380
other info that might help us debug this:
context-{5:5}
4 locks held by migration/2/20:
#0: ffff91622a3ff4c0 (&irq_desc_lock_class){-.-.}-{2:2}, at:
irq_migrate_all_off_this_cpu+0x41/0x2f0
#1: ffffffffb2c509b8 (vector_lock){-.-.}-{2:2}, at:
irq_force_complete_move+0x2a/0x70
#2: ffffffffb2c7cec0 (console_lock){+.+.}-{0:0}, at: printk+0x48/0x4a
#3: ffffffffb2c7cbe0 (console_owner){....}-{0:0}, at:
console_unlock+0x1af/0x650
stack backtrace:
CPU: 2 PID: 20 Comm: migration/2 Not tainted 5.9.0-rc5+ #3
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-2.fc32
04/01/2014
Call Trace:
dump_stack+0x8b/0xb8
__lock_acquire.cold+0x1ce/0x333
? stack_trace_save+0x3b/0x50
? save_trace+0x3f/0x360
lock_acquire+0xbf/0x3e0
? serial8250_console_write+0x8e/0x380
_raw_spin_lock_irqsave+0x48/0x60
? serial8250_console_write+0x8e/0x380
serial8250_console_write+0x8e/0x380
? console_unlock+0x1e8/0x650
console_unlock+0x3f3/0x650
? printk+0x48/0x4a
vprintk_emit+0x1b1/0x440
printk+0x48/0x4a
irq_force_complete_move.cold+0xf/0x14
irq_migrate_all_off_this_cpu+0xfa/0x2f0
fixup_irqs+0x25/0xe8
cpu_disable_common+0x2b8/0x2d0
native_cpu_disable+0x18/0x30
take_cpu_down+0x2f/0xa0
multi_cpu_stop+0x6d/0x130
? stop_machine_yield+0x10/0x10
cpu_stopper_thread+0x7b/0x110
? smpboot_thread_fn+0x26/0x1e0
smpboot_thread_fn+0x10b/0x1e0
? smpboot_register_percpu_thread+0xf0/0xf0
kthread+0x13a/0x150
? kthread_create_worker_on_cpu+0x40/0x40
ret_from_fork+0x22/0x30
smpboot: CPU 2 is now offline
=============================
It was caused by printk() inside a code section protected by a
raw_spin_lock() that ended up calling a serial console that
uses a regular spin_lock().
Use the printk_deferred() to avoid calling the serial console
in a raw_spin_lock() protected section.
Signed-off-by: Daniel Bristot de Oliveira <bris...@redhat.com>
Suggested-by: Thomas Gleixner <t...@linutronix.de>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Ingo Molnar <mi...@redhat.com>
Cc: Borislav Petkov <b...@alien8.de>
Cc: "H. Peter Anvin" <h...@zytor.com>
Cc: Marc Zyngier <m...@kernel.org>
Cc: Peter Xu <pet...@redhat.com>
Cc: Andy Lutomirski <l...@kernel.org>
Cc: Bjorn Helgaas <bhelg...@google.com>
Cc: x...@kernel.org
Cc: linux-kernel@vger.kernel.org
---
arch/x86/kernel/apic/vector.c | 20 ++++++++++++--------
1 file changed, 12 insertions(+), 8 deletions(-)
diff --git a/arch/x86/kernel/apic/vector.c b/arch/x86/kernel/apic/vector.c
index f8a56b5dc29f..1a0e5535b8ac 100644
--- a/arch/x86/kernel/apic/vector.c
+++ b/arch/x86/kernel/apic/vector.c
@@ -406,8 +406,9 @@ static int activate_reserved(struct irq_data *irqd)
*/
if (!cpumask_subset(irq_data_get_effective_affinity_mask(irqd),
irq_data_get_affinity_mask(irqd))) {
- pr_warn("irq %u: Affinity broken due to vector space
exhaustion.\n",
- irqd->irq);
+ printk_deferred(KERN_WARNING
+ "irq %u: Affinity broken due to vector space
exhaustion.\n",
+ irqd->irq);
}
return ret;
@@ -1012,8 +1013,9 @@ void irq_force_complete_move(struct irq_desc *desc)
* so we have the necessary information when a problem in that
* area arises.
*/
- pr_warn("IRQ fixup: irq %d move in progress, old vector %d\n",
- irqd->irq, vector);
+ printk_deferred(KERN_WARNING
+ "IRQ fixup: irq %d move in progress, old vector
%d\n",
+ irqd->irq, vector);
}
free_moved_vector(apicd);
unlock:
@@ -1034,15 +1036,17 @@ int lapic_can_unplug_cpu(void)
tomove = irq_matrix_allocated(vector_matrix);
avl = irq_matrix_available(vector_matrix, true);
if (avl < tomove) {
- pr_warn("CPU %u has %u vectors, %u available. Cannot disable
CPU\n",
- cpu, tomove, avl);
+ printk_deferred(KERN_WARNING
+ "CPU %u has %u vectors, %u available. Cannot
disable CPU\n",
+ cpu, tomove, avl);
ret = -ENOSPC;
goto out;
}
rsvd = irq_matrix_reserved(vector_matrix);
if (avl < rsvd) {
- pr_warn("Reserved vectors %u > available %u. IRQ request may
fail\n",
- rsvd, avl);
+ printk_deferred(KERN_WARNING
+ "Reserved vectors %u > available %u. IRQ
request may fail\n",
+ rsvd, avl);
}
out:
raw_spin_unlock(&vector_lock);
--
2.26.2
