Patch "ARM: 9317/1: kexec: Make smp stop calls asynchronous" has been added to the 6.1-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    ARM: 9317/1: kexec: Make smp stop calls asynchronous

to the 6.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     arm-9317-1-kexec-make-smp-stop-calls-asynchronous.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 4090d1bf30dece5c330c4897d2e61dd824378693
Author: Mårten Lindahl <marten.lindahl@xxxxxxxx>
Date:   Tue Aug 8 09:37:32 2023 +0100

    ARM: 9317/1: kexec: Make smp stop calls asynchronous
    
    [ Upstream commit 8922ba71c969d2a0c01a94372a71477d879470de ]
    
    If a panic is triggered by a hrtimer interrupt all online cpus will be
    notified and set offline. But as highlighted by commit 19dbdcb8039c
    ("smp: Warn on function calls from softirq context") this call should
    not be made synchronous with disabled interrupts:
    
     softdog: Initiating panic
     Kernel panic - not syncing: Software Watchdog Timer expired
     WARNING: CPU: 1 PID: 0 at kernel/smp.c:753 smp_call_function_many_cond
       unwind_backtrace:
         show_stack
         dump_stack_lvl
         __warn
         warn_slowpath_fmt
         smp_call_function_many_cond
         smp_call_function
         crash_smp_send_stop.part.0
         machine_crash_shutdown
         __crash_kexec
         panic
         softdog_fire
         __hrtimer_run_queues
         hrtimer_interrupt
    
    Make the smp call for machine_crash_nonpanic_core() asynchronous.
    
    Signed-off-by: Mårten Lindahl <marten.lindahl@xxxxxxxx>
    Signed-off-by: Russell King (Oracle) <rmk+kernel@xxxxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/arch/arm/kernel/machine_kexec.c b/arch/arm/kernel/machine_kexec.c
index f567032a09c0b..6d1938d1b4df7 100644
--- a/arch/arm/kernel/machine_kexec.c
+++ b/arch/arm/kernel/machine_kexec.c
@@ -92,16 +92,28 @@ void machine_crash_nonpanic_core(void *unused)
 	}
 }
 
+static DEFINE_PER_CPU(call_single_data_t, cpu_stop_csd) =
+	CSD_INIT(machine_crash_nonpanic_core, NULL);
+
 void crash_smp_send_stop(void)
 {
 	static int cpus_stopped;
 	unsigned long msecs;
+	call_single_data_t *csd;
+	int cpu, this_cpu = raw_smp_processor_id();
 
 	if (cpus_stopped)
 		return;
 
 	atomic_set(&waiting_for_crash_ipi, num_online_cpus() - 1);
-	smp_call_function(machine_crash_nonpanic_core, NULL, false);
+	for_each_online_cpu(cpu) {
+		if (cpu == this_cpu)
+			continue;
+
+		csd = &per_cpu(cpu_stop_csd, cpu);
+		smp_call_function_single_async(cpu, csd);
+	}
+
 	msecs = 1000; /* Wait at most a second for the other cpus to stop */
 	while ((atomic_read(&waiting_for_crash_ipi) > 0) && msecs) {
 		mdelay(1);