Re: [PATCH REPOST] alpha: Replace bogus in_interrupt()

[Serge Belyshev <belyshev@depni.sinp.msu.ru>]

Andrew Morton <akpm@linux-foundation.org> writes:

> On Fri, 13 Nov 2020 14:58:32 +0100 Sebastian Andrzej Siewior <bigeasy@linutronix.de> wrote:
>
>> From: Thomas Gleixner <tglx@linutronix.de>
>> 
>> in_interrupt() is true for a variety of things including bottom half
>> disabled regions. Deducing hard interrupt context from it is dubious at
>> best.
>> 
>> Use in_irq() which is true if called in hard interrupt context. Otherwise
>> calling irq_exit() would do more harm than good.
>> 
>
> Gee, how to test it.  Does anyone run current kernels on alpha?

Hold my beer:

--- a/arch/alpha/kernel/process.c
+++ b/arch/alpha/kernel/process.c
@@ -134,8 +134,10 @@ common_shutdown_1(void *generic_ptr)
 #ifdef CONFIG_DUMMY_CONSOLE
                /* If we've gotten here after SysRq-b, leave interrupt
                   context before taking over the console. */
-               if (in_irq())
+               if (in_irq()) {
+                       printk ("in_irq(): true\n");
                        irq_exit();
+               }
                /* This has the effect of resetting the VGA video origin.  */
                console_lock();
                do_take_over_console(&dummy_con, 0, MAX_NR_CONSOLES-1, 1);


and then sysrq-b over serial console:

[   56.531250] sysrq: Resetting
[   56.531250] in_irq(): true
[   56.531250] Console: switching to colour dummy device 80x25

halted CPU 0

halt code = 5
HALT instruction executed
PC = fffffc0000310040
Resetting I/O buses...
>>>

Tested-by: Serge Belyshev <belyshev@depni.sinp.msu.ru>