Re: [PATCH] Fix scheduling-while-atomic problem in console_cpu_notify()

Paul E. McKenney
2012-10-16T04:36:11Z

On Mon, Oct 15, 2012 at 05:31:28PM -0700, Paul E. McKenney wrote:
> The console_cpu_notify( function runs with interrupts disabled in
> the CPU_DEAD case. It therefore cannot block, for example, as will
> happen when it calls console_lock(). Therefore, remove the CPU_DEAD
> leg of the switch statement to avoid this problem.
>
> Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>

s/CPU_DEAD/CPU_DYING/

Apparently it is a bad idea to compose and send a patch while in a
C++ standards committee meeting where people are arguing about async
futures... Fixed patch below.

Thanx, Paul

------------------------------------------------------------------------

printk: Fix scheduling-while-atomic problem in console_cpu_notify()

The console_cpu_notify( function runs with interrupts disabled in
the CPU_DYING case. It therefore cannot block, for example, as will
happen when it calls console_lock(). Therefore, remove the CPU_DYING
leg of the switch statement to avoid this problem.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

diff --git a/kernel/printk.c b/kernel/printk.c
index 66a2ea3..2d607f4 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -1890,7 +1890,6 @@ static int __cpuinit console_cpu_notify(struct notifier_block *self,
switch (action) {
case CPU_ONLINE:
case CPU_DEAD:
- case CPU_DYING:
case CPU_DOWN_FAILED:
case CPU_UP_CANCELED:
console_lock();