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Re: [Xen-devel] [PATCH] Xen: Force non-irq keyhandler to be run in tasklet when receive a debugkey from serial port





On 10/24/2016 6:53 PM, Jan Beulich wrote:
On 22.10.16 at 13:23, <tianyu.lan@xxxxxxxxx> wrote:
__serial_rx() runs in either irq handler or timer handler and non-irq
keyhandler should not run in these contexts. So always force non-irq
keyhandler to run in tasklet when receive a debugkey from serial port

Signed-off-by: Lan Tianyu <tianyu.lan@xxxxxxxxx>
---
 xen/drivers/char/console.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
index b0f74ce..184b523 100644
--- a/xen/drivers/char/console.c
+++ b/xen/drivers/char/console.c
@@ -347,7 +347,7 @@ static void switch_serial_input(void)
 static void __serial_rx(char c, struct cpu_user_regs *regs)
 {
     if ( xen_rx )
-        return handle_keypress(c, regs, !in_irq());
+        return handle_keypress(c, regs, true);

Together with one of your earlier patches having got reverted, I
think we need to take a step back here instead of going back to
what was requested to be changed from v2 of the original patch.
In particular I assume that the problem you're trying to address is
not limited to dump_timerq() - at least dump_runq() should be as
problematic on many-CPU systems.

I think the issue here is that my previous patch commit
610b4eda2c("keyhandler: rework process of nonirq keyhandler") makes
non-irq keyhandler run in irq context. This is caused by input param
"!in_irq()" which is false in irq context. handle_keypress() runs keyhandler synchronically. This patch fixes the issue.


I think (and I vaguely recall possibly having said so during earlier
review) that dump functions the output of which depends on CPU
count should get modeled after dump_registers(), and it might be
worth abstracting this in keyhandler.c.

Yes, but this sounds like a new feature or framework rework rather than a fix patch.


In any case quite likely the
other patch of yours (which the one here basically modifies) may
then also want to be reverted.

I think patch "timer: process softirq during dumping timer"
does right thing. The issue is triggered by previous patch.


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