watchdog/hardlockup: avoid large stack frames in watchdog_hardlockup_check()

After commit 77c12fc95980 ("watchdog/hardlockup: add a "cpu" param to
watchdog_hardlockup_check()") we started storing a `struct cpumask` on the
stack in watchdog_hardlockup_check().  On systems with CONFIG_NR_CPUS set
to 8192 this takes up 1K on the stack.  That triggers warnings with
`CONFIG_FRAME_WARN` set to 1024.

We'll use the new trigger_allbutcpu_cpu_backtrace() to avoid needing to
use a CPU mask at all.

Link: https://lkml.kernel.org/r/20230804065935.v4.2.I501ab68cb926ee33a7c87e063d207abf09b9943c@changeid
Fixes: 77c12fc95980 ("watchdog/hardlockup: add a "cpu" param to watchdog_hardlockup_check()")
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/r/202307310955.pLZDhpnl-lkp@intel.com
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Cc: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: Pingfan Liu <kernelfans@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 085d7a7..d145305 100644 (file)
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -151,9 +151,6 @@ void watchdog_hardlockup_check(unsigned int cpu, struct pt_regs *regs)
         */
        if (is_hardlockup(cpu)) {
                unsigned int this_cpu = smp_processor_id();
-               struct cpumask backtrace_mask;
-
-               cpumask_copy(&backtrace_mask, cpu_online_mask);
 
                /* Only print hardlockups once. */
                if (per_cpu(watchdog_hardlockup_warned, cpu))
@@ -167,10 +164,8 @@ void watchdog_hardlockup_check(unsigned int cpu, struct pt_regs *regs)
                                show_regs(regs);
                        else
                                dump_stack();
-                       cpumask_clear_cpu(cpu, &backtrace_mask);
                } else {
-                       if (trigger_single_cpu_backtrace(cpu))
-                               cpumask_clear_cpu(cpu, &backtrace_mask);
+                       trigger_single_cpu_backtrace(cpu);
                }
 
                /*
@@ -179,7 +174,7 @@ void watchdog_hardlockup_check(unsigned int cpu, struct pt_regs *regs)
                 */
                if (sysctl_hardlockup_all_cpu_backtrace &&
                    !test_and_set_bit(0, &watchdog_hardlockup_all_cpu_dumped))
-                       trigger_cpumask_backtrace(&backtrace_mask);
+                       trigger_allbutcpu_cpu_backtrace(cpu);
 
                if (hardlockup_panic)
                        nmi_panic(regs, "Hard LOCKUP");