From 233756a640be811efae33763db718fe29753b1e9 Mon Sep 17 00:00:00 2001 From: Feng Tang Date: Wed, 7 Jun 2023 15:54:33 +0800 Subject: [PATCH] x86/tsc: Extend watchdog check exemption to 4-Sockets platform There were reports again that the tsc clocksource on 4 sockets x86 servers was wrongly judged as 'unstable' by 'jiffies' and other watchdogs, and disabled [1][2]. Commit b50db7095fe0 ("x86/tsc: Disable clocksource watchdog for TSC on qualified platorms") was introduce to deal with these false alarms of tsc unstable issues, covering qualified platforms for 2 sockets or smaller ones. And from history of chasing TSC issues, Thomas and Peter only saw real TSC synchronization issue on 8 socket machines. So extend the exemption to 4 sockets to fix the issue. Rui also proposed another way to disable 'jiffies' as clocksource watchdog [3], which can also solve problem in [1]. in an architecture independent way, but can't cure the problem in [2]. whose watchdog is HPET or PMTIMER, while 'jiffies' is mostly used as watchdog in boot phase. 'nr_online_nodes' has known inaccurate problem for cases like platform with cpu-less memory nodes, sub numa cluster enabled, fakenuma, kernel cmdline parameter 'maxcpus=', etc. The harmful case is the 'maxcpus' one which could possibly under estimates the package number, and disable the watchdog, but bright side is it is mostly for debug usage. All these will be addressed in other patches, as discussed in thread [4]. [1]. https://lore.kernel.org/all/9d3bf570-3108-0336-9c52-9bee15767d29@huawei.com/ [2]. https://lore.kernel.org/lkml/06df410c-2177-4671-832f-339cff05b1d9@paulmck-laptop/ [3]. https://lore.kernel.org/all/bd5b97f89ab2887543fc262348d1c7cafcaae536.camel@intel.com/ [4]. https://lore.kernel.org/all/20221021062131.1826810-1-feng.tang@intel.com/ Reported-by: Yu Liao Reported-by: Paul E. McKenney Signed-off-by: Feng Tang Signed-off-by: Paul E. McKenney --- arch/x86/kernel/tsc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 3425c6a943e4..15f97c0abc9d 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -1258,7 +1258,7 @@ static void __init check_system_tsc_reliable(void) if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) && boot_cpu_has(X86_FEATURE_NONSTOP_TSC) && boot_cpu_has(X86_FEATURE_TSC_ADJUST) && - nr_online_nodes <= 2) + nr_online_nodes <= 4) tsc_disable_clocksource_watchdog(); }