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Subject[RFC PATCH v3 05/12] arm64: smp: use generic SMP stop common code
Date
Make arm64 use the generic SMP-stop logic provided by common code
unified smp_send_stop() function.

arm64 smp_send_stop() logic had a bug in it: it failed to consider the
online status of the calling CPU when evaluating if any stop message
needed to be sent to other CPus at all: this resulted, on a 2-CPUs
system, in the failure to stop all cpus if one paniced while starting
up, leaving such system in an unexpected lively state.

[root@arch ~]# echo 1 > /sys/devices/system/cpu/cpu1/online
[root@arch ~]# [ 152.583368] ------------[ cut here ]------------
[ 152.583872] kernel BUG at arch/arm64/kernel/cpufeature.c:852!
[ 152.584693] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
[ 152.585228] Modules linked in:
[ 152.586040] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.3.0-rc5-00001-gcabd12118c4a-dirty #2
[ 152.586218] Hardware name: Foundation-v8A (DT)
[ 152.586478] pstate: 000001c5 (nzcv dAIF -PAN -UAO)
[ 152.587260] pc : has_cpuid_feature+0x35c/0x360
[ 152.587398] lr : verify_local_elf_hwcaps+0x6c/0xf0
[ 152.587520] sp : ffff0000118bbf60
[ 152.587605] x29: ffff0000118bbf60 x28: 0000000000000000
[ 152.587784] x27: 0000000000000000 x26: 0000000000000000
[ 152.587882] x25: ffff00001167a010 x24: ffff0000112f59f8
[ 152.587992] x23: 0000000000000000 x22: 0000000000000000
[ 152.588085] x21: ffff0000112ea018 x20: ffff000010fe5518
[ 152.588180] x19: ffff000010ba3f30 x18: 0000000000000036
[ 152.588285] x17: 0000000000000000 x16: 0000000000000000
[ 152.588380] x15: 0000000000000000 x14: ffff80087a821210
[ 152.588481] x13: 0000000000000000 x12: 0000000000000000
[ 152.588599] x11: 0000000000000080 x10: 00400032b5503510
[ 152.588709] x9 : 0000000000000000 x8 : ffff000010b93204
[ 152.588810] x7 : 00000000800001d8 x6 : 0000000000000005
[ 152.588910] x5 : 0000000000000000 x4 : 0000000000000000
[ 152.589021] x3 : 0000000000000000 x2 : 0000000000008000
[ 152.589121] x1 : 0000000000180480 x0 : 0000000000180480
[ 152.589379] Call trace:
[ 152.589646] has_cpuid_feature+0x35c/0x360
[ 152.589763] verify_local_elf_hwcaps+0x6c/0xf0
[ 152.589858] check_local_cpu_capabilities+0x88/0x118
[ 152.589968] secondary_start_kernel+0xc4/0x168
[ 152.590530] Code: d53801e0 17ffff58 d5380600 17ffff56 (d4210000)
[ 152.592215] ---[ end trace 80ea98416149c87e ]---
[ 152.592734] Kernel panic - not syncing: Attempted to kill the idle task!
[ 152.593173] Kernel Offset: disabled
[ 152.593501] CPU features: 0x0004,20c02008
[ 152.593678] Memory Limit: none
[ 152.594208] ---[ end Kernel panic - not syncing: Attempted to kill the idle
task! ]---
[root@arch ~]# bash: echo: write error: Input/output error
[root@arch ~]#
[root@arch ~]#
[root@arch ~]# echo HELO
HELO

Get rid of such bug, switching arm64 to use the common SMP stop code.

Reported-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
---
v1 --> v2
- now selecting arch/Kconfig ARCH_USE_COMMON_SMP_STOP
- added attempt_num arch_smp_stop_call() helper
---
arch/arm64/Kconfig | 1 +
arch/arm64/kernel/smp.c | 29 ++++++-----------------------
2 files changed, 7 insertions(+), 23 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index b1b4476ddb83..618e2c2052dd 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -64,6 +64,7 @@ config ARM64
select ARCH_USE_CMPXCHG_LOCKREF
select ARCH_USE_QUEUED_RWLOCKS
select ARCH_USE_QUEUED_SPINLOCKS
+ select ARCH_USE_COMMON_SMP_STOP
select ARCH_SUPPORTS_MEMORY_FAILURE
select ARCH_SUPPORTS_ATOMIC_RMW
select ARCH_SUPPORTS_INT128 if CC_HAS_INT128 && (GCC_VERSION >= 50000 || CC_IS_CLANG)
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index d4ed9a19d8fe..7c1869161b5e 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -958,33 +958,16 @@ void tick_broadcast(const struct cpumask *mask)
}
#endif

-void smp_send_stop(void)
+void arch_smp_cpus_stop_complete(void)
{
- unsigned long timeout;
-
- if (num_online_cpus() > 1) {
- cpumask_t mask;
-
- cpumask_copy(&mask, cpu_online_mask);
- cpumask_clear_cpu(smp_processor_id(), &mask);
-
- if (system_state <= SYSTEM_RUNNING)
- pr_crit("SMP: stopping secondary CPUs\n");
- smp_cross_call(&mask, IPI_CPU_STOP);
- }
-
- /* Wait up to one second for other CPUs to stop */
- timeout = USEC_PER_SEC;
- while (num_online_cpus() > 1 && timeout--)
- udelay(1);
-
- if (num_online_cpus() > 1)
- pr_warn("SMP: failed to stop secondary CPUs %*pbl\n",
- cpumask_pr_args(cpu_online_mask));
-
sdei_mask_local_cpu();
}

+void arch_smp_stop_call(cpumask_t *cpus, unsigned int __unused)
+{
+ smp_cross_call(cpus, IPI_CPU_STOP);
+}
+
#ifdef CONFIG_KEXEC_CORE
void crash_smp_send_stop(void)
{
--
2.17.1
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