[PATCH 4.9 186/240] powerpc/pseries: Stop calling printk in rtas_stop_self()

Greg Kroah-Hartman
2021-05-20T11:24:24Z

From: Michael Ellerman <mpe@ellerman.id.au>

[ Upstream commit ed8029d7b472369a010a1901358567ca3b6dbb0d ]

RCU complains about us calling printk() from an offline CPU:

=============================
WARNING: suspicious RCU usage
5.12.0-rc7-02874-g7cf90e481cb8 #1 Not tainted
-----------------------------
kernel/locking/lockdep.c:3568 RCU-list traversed in non-reader section!!

other info that might help us debug this:

RCU used illegally from offline CPU!
rcu_scheduler_active = 2, debug_locks = 1
no locks held by swapper/0/0.

stack backtrace:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.12.0-rc7-02874-g7cf90e481cb8 #1
Call Trace:
dump_stack+0xec/0x144 (unreliable)
lockdep_rcu_suspicious+0x124/0x144
__lock_acquire+0x1098/0x28b0
lock_acquire+0x128/0x600
_raw_spin_lock_irqsave+0x6c/0xc0
down_trylock+0x2c/0x70
__down_trylock_console_sem+0x60/0x140
vprintk_emit+0x1a8/0x4b0
vprintk_func+0xcc/0x200
printk+0x40/0x54
pseries_cpu_offline_self+0xc0/0x120
arch_cpu_idle_dead+0x54/0x70
do_idle+0x174/0x4a0
cpu_startup_entry+0x38/0x40
rest_init+0x268/0x388
start_kernel+0x748/0x790
start_here_common+0x1c/0x614

Which happens because by the time we get to rtas_stop_self() we are
already offline. In addition the message can be spammy, and is not that
helpful for users, so remove it.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210418135413.1204031-1-mpe@ellerman.id.au
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/powerpc/platforms/pseries/hotplug-cpu.c | 3 ---
1 file changed, 3 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/hotplug-cpu.c b/arch/powerpc/platforms/pseries/hotplug-cpu.c
index 7a2beedb9740..a7d9dd029850 100644
--- a/arch/powerpc/platforms/pseries/hotplug-cpu.c
+++ b/arch/powerpc/platforms/pseries/hotplug-cpu.c
@@ -92,9 +92,6 @@ static void rtas_stop_self(void)

BUG_ON(rtas_stop_self_token == RTAS_UNKNOWN_SERVICE);

- printk("cpu %u (hwid %u) Ready to die...\n",
- smp_processor_id(), hard_smp_processor_id());
-
rtas_call_unlocked(&args, rtas_stop_self_token, 0, 1, NULL);

panic("Alas, I survived.\n");
--
2.30.2