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Message-Id: <20190913181953.45748-10-cristian.marussi@arm.com>
Date: Fri, 13 Sep 2019 19:19:50 +0100
From: Cristian Marussi <cristian.marussi@....com>
To: linux-kernel@...r.kernel.org
Cc: linux-arch@...r.kernel.org, mark.rutland@....com,
peterz@...radead.org, catalin.marinas@....com,
takahiro.akashi@...aro.org, james.morse@....com,
hidehiro.kawai.ez@...achi.com, tglx@...utronix.de, will@...nel.org,
dave.martin@....com, linux-arm-kernel@...ts.infradead.org,
mingo@...hat.com, x86@...nel.org, dzickus@...hat.com,
ehabkost@...hat.com, linux@...linux.org.uk, davem@...emloft.net,
sparclinux@...r.kernel.org, hch@...radead.org
Subject: [RFC PATCH v2 09/12] x86: smp: use SMP crash-stop common code
Make x86 use the SMP common implementation of crash_smp_send_stop() and
its generic logic, by removing the x86 crash_smp_send_stop() definition
and providing the needed arch specific helpers.
Remove also redundant smp_ops.crash_stop_other_cpus(); add shared util
function common_nmi_shootdown_cpus(), which is a generalization of the
previous nmi_shootdown_cpus(), and it is used by architecture backend
helper arch_smp_crash_call().
Modify original crash_nmi_callback() to properly set cpu offline flag
and adding needed memory barriers.
Modify original nmi_shootdown_cpus() to rely on common code logic
provided by generic crash_smp_send_stop(): this was needed because the
original nmi_shootdown_cpus() was used also on the emergency reboot
path, employing a different callback. Reuse the same shootdown_callback
mechanism to properly handle both a crash and an emergency reboot through
the same common code crash path.
Signed-off-by: Cristian Marussi <cristian.marussi@....com>
---
Note that in this patch we kept in use the original x86 local handling
of 'crashing_cpu' variable:
crashing_cpu = safe_smp_processor_id();
Instead, common SMP stop code could have been easily extended to keep and
expose to architectures backends such value using some additional helper
like smp_stop_get_stopping_cpu_id().
This has not been addressed in this series.
---
arch/x86/include/asm/reboot.h | 2 ++
arch/x86/include/asm/smp.h | 1 -
arch/x86/kernel/crash.c | 27 ++++---------------
arch/x86/kernel/reboot.c | 50 ++++++++++++++++++++++-------------
arch/x86/kernel/smp.c | 3 ---
5 files changed, 38 insertions(+), 45 deletions(-)
diff --git a/arch/x86/include/asm/reboot.h b/arch/x86/include/asm/reboot.h
index 04c17be9b5fd..a1a9cbed6df5 100644
--- a/arch/x86/include/asm/reboot.h
+++ b/arch/x86/include/asm/reboot.h
@@ -3,6 +3,7 @@
#define _ASM_X86_REBOOT_H
#include <linux/kdebug.h>
+#include <linux/cpumask.h>
struct pt_regs;
@@ -28,6 +29,7 @@ void __noreturn machine_real_restart(unsigned int type);
typedef void (*nmi_shootdown_cb)(int, struct pt_regs*);
void nmi_panic_self_stop(struct pt_regs *regs);
void nmi_shootdown_cpus(nmi_shootdown_cb callback);
+void common_nmi_shootdown_cpus(cpumask_t *cpus, nmi_shootdown_cb callback);
void run_crash_ipi_callback(struct pt_regs *regs);
#endif /* _ASM_X86_REBOOT_H */
diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
index 5cf590259d68..684643ad71e4 100644
--- a/arch/x86/include/asm/smp.h
+++ b/arch/x86/include/asm/smp.h
@@ -49,7 +49,6 @@ struct smp_ops {
void (*smp_cpus_done)(unsigned max_cpus);
void (*stop_other_cpus)(int wait);
- void (*crash_stop_other_cpus)(void);
void (*smp_send_reschedule)(int cpu);
int (*cpu_up)(unsigned cpu, struct task_struct *tidle);
diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index 2bf70a2fed90..8fff06c7cd26 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -96,34 +96,16 @@ static void kdump_nmi_callback(int cpu, struct pt_regs *regs)
disable_local_APIC();
}
-void kdump_nmi_shootdown_cpus(void)
+void arch_smp_crash_call(cpumask_t *cpus, unsigned int __unused)
{
- nmi_shootdown_cpus(kdump_nmi_callback);
-
- disable_local_APIC();
+ common_nmi_shootdown_cpus(cpus, kdump_nmi_callback);
}
-/* Override the weak function in kernel/panic.c */
-void crash_smp_send_stop(void)
+void arch_smp_cpus_crash_complete(void)
{
- static int cpus_stopped;
-
- if (cpus_stopped)
- return;
-
- if (smp_ops.crash_stop_other_cpus)
- smp_ops.crash_stop_other_cpus();
- else
- smp_send_stop();
-
- cpus_stopped = 1;
+ disable_local_APIC();
}
-#else
-void crash_smp_send_stop(void)
-{
- /* There are no cpus to shootdown */
-}
#endif
void native_machine_crash_shutdown(struct pt_regs *regs)
@@ -139,6 +121,7 @@ void native_machine_crash_shutdown(struct pt_regs *regs)
/* The kernel is broken so disable interrupts */
local_irq_disable();
+ /* calling into SMP common stop code */
crash_smp_send_stop();
/*
diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
index 09d6bded3c1e..69f894e28fec 100644
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -799,7 +799,6 @@ int crashing_cpu = -1;
static nmi_shootdown_cb shootdown_callback;
-static atomic_t waiting_for_crash_ipi;
static int crash_ipi_issued;
static int crash_nmi_callback(unsigned int val, struct pt_regs *regs)
@@ -819,7 +818,12 @@ static int crash_nmi_callback(unsigned int val, struct pt_regs *regs)
shootdown_callback(cpu, regs);
- atomic_dec(&waiting_for_crash_ipi);
+ /* ensure all shootdown writes are visible once cpu is seen offline */
+ smp_wmb();
+ set_cpu_online(cpu, false);
+ /* ensure all writes are globally visible before cpu parks */
+ wmb();
+
/* Assume hlt works */
halt();
for (;;)
@@ -828,29 +832,44 @@ static int crash_nmi_callback(unsigned int val, struct pt_regs *regs)
return NMI_HANDLED;
}
-static void smp_send_nmi_allbutself(void)
-{
- apic->send_IPI_allbutself(NMI_VECTOR);
-}
-
/*
* Halt all other CPUs, calling the specified function on each of them
*
* This function can be used to halt all other CPUs on crash
* or emergency reboot time. The function passed as parameter
* will be called inside a NMI handler on all CPUs.
+ *
+ * It relies on crash_smp_send_stop() common code logic to shutdown CPUs.
*/
void nmi_shootdown_cpus(nmi_shootdown_cb callback)
{
- unsigned long msecs;
+ local_irq_disable();
+
+ shootdown_callback = callback;
+ /* ensure callback in place before calling into common crash code */
+ wmb();
+ /* call into common SMP Crash Stop to reuse the logic */
+ crash_smp_send_stop();
+}
+
+/*
+ * Halt the specified @cpus, calling the provided @callback on each of them
+ * unless a shootdown_callback was already installed previously: this way
+ * we can handle here also the emergency reboot requests issued via
+ * nmi_shootdown_cpus() and routed via usual common code crash_smp_send_stop()
+ *
+ * Called by arch_smp_crash_call() arch-helper.
+ */
+void common_nmi_shootdown_cpus(cpumask_t *cpus, nmi_shootdown_cb callback)
+{
local_irq_disable();
/* Make a note of crashing cpu. Will be used in NMI callback. */
crashing_cpu = safe_smp_processor_id();
- shootdown_callback = callback;
-
- atomic_set(&waiting_for_crash_ipi, num_online_cpus() - 1);
+ /* skip when the callback has been already set by nmi_shootdown_cpus */
+ if (!shootdown_callback)
+ shootdown_callback = callback;
/* Would it be better to replace the trap vector here? */
if (register_nmi_handler(NMI_LOCAL, crash_nmi_callback,
NMI_FLAG_FIRST, "crash"))
@@ -860,18 +879,11 @@ void nmi_shootdown_cpus(nmi_shootdown_cb callback)
* out the NMI
*/
wmb();
-
- smp_send_nmi_allbutself();
+ apic->send_IPI_mask(cpus, NMI_VECTOR);
/* Kick CPUs looping in NMI context. */
WRITE_ONCE(crash_ipi_issued, 1);
- msecs = 1000; /* Wait at most a second for the other cpus to stop */
- while ((atomic_read(&waiting_for_crash_ipi) > 0) && msecs) {
- mdelay(1);
- msecs--;
- }
-
/* Leave the nmi callback set */
}
diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c
index 0942cae46fee..d718b185c6a9 100644
--- a/arch/x86/kernel/smp.c
+++ b/arch/x86/kernel/smp.c
@@ -295,9 +295,6 @@ struct smp_ops smp_ops = {
.smp_cpus_done = native_smp_cpus_done,
.stop_other_cpus = native_stop_other_cpus,
-#if defined(CONFIG_KEXEC_CORE)
- .crash_stop_other_cpus = kdump_nmi_shootdown_cpus,
-#endif
.smp_send_reschedule = native_smp_send_reschedule,
.cpu_up = native_cpu_up,
--
2.17.1
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