[xen staging] x86/console: process softirqs between warning prints

[patchbot@xxxxxxx]

commit 6bd1b4d35c05c21a78bf00f610587ce8a75cb5c2
Author:     Roger Pau Monné <roger.pau@xxxxxxxxxx>
AuthorDate: Fri Feb 18 09:02:16 2022 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Feb 18 09:02:16 2022 +0100

    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@xxxxxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/common/warning.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/xen/common/warning.c b/xen/common/warning.c
index 0269c6715c..e6e1404baf 100644
--- 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++ )
--
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