x86/console: process softirqs between warning prints

Process softirqs while printing end of boot warnings. Each warning can
be several lines long, and on slow consoles printing multiple ones
without processing softirqs can result in the watchdog triggering:

(XEN) [   22.277806] ***************************************************
(XEN) [   22.417802] WARNING: CONSOLE OUTPUT IS SYNCHRONOUS
(XEN) [   22.556029] This option is intended to aid debugging of Xen by ensuring
(XEN) [   22.696802] that all output is synchronously delivered on the serial line.
(XEN) [   22.838024] However it can introduce SIGNIFICANT latencies and affect
(XEN) [   22.978710] timekeeping. It is NOT recommended for production use!
(XEN) [   23.119066] ***************************************************
(XEN) [   23.258865] Booted on L1TF-vulnerable hardware with SMT/Hyperthreading
(XEN) [   23.399560] enabled.  Please assess your configuration and choose an
(XEN) [   23.539925] explicit 'smt=<bool>' setting.  See XSA-273.
(XEN) [   23.678860] ***************************************************
(XEN) [   23.818492] Booted on MLPDS/MFBDS-vulnerable hardware with SMT/Hyperthreading
(XEN) [   23.959811] enabled.  Mitigations will not be fully effective.  Please
(XEN) [   24.100396] choose an explicit smt=<bool> setting.  See XSA-297.
(XEN) [   24.240254] *************************************************(XEN) [   24.247302] Watchdog timer detects that CPU0 is stuck!
(XEN) [   24.386785] ----[ Xen-4.17-unstable  x86_64  debug=y  Tainted:   C    ]----
(XEN) [   24.527874] CPU:    0
(XEN) [   24.662422] RIP:    e008:[<ffff82d04025b84a>] drivers/char/ns16550.c#ns16550_tx_ready+0x3a/0x90

Fixes: ee3fd57acd ('xen: add warning infrastructure')
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
master commit: 6bd1b4d35c05c21a78bf00f610587ce8a75cb5c2
master date: 2022-02-18 09:02:16 +0100

diff --git a/xen/common/warning.c b/xen/common/warning.c
index 0269c6715c85f6d3ef1d2a9f39c178a34fb34194..e6e1404baf560e0a01e854549df9e0f61597e85c 100644 (file)
--- a/xen/common/warning.c
+++ b/xen/common/warning.c
@@ -30,6 +30,7 @@ void __init warning_print(void)
     {
         printk("%s", warnings[i]);
         printk("***************************************************\n");
+        process_pending_softirqs();
     }
 
     for ( i = 0; i < 3; i++ )