[PATCH v2 2/2] Do not change worker's running cpu in cmci_rediscover().

From: Tang Chen
Date: Fri Oct 19 2012 - 01:46:28 EST


cmci_rediscover() used set_cpus_allowed_ptr() to change the current process's
running cpu, and migrate itself to the dest cpu. But worker processes are not
allowed to be migrated. If current is a worker, the worker will be migrated to
another cpu, but the corresponding worker_pool is still on the original cpu.

In this case, the following BUG_ON in try_to_wake_up_local() will be triggered:
BUG_ON(rq != this_rq());

This will cause the kernel panic.

This patch removes the set_cpus_allowed_ptr() call, and put the cmci rediscover
jobs onto all the other cpus using system_wq. This could bring some delay for
the jobs.

Signed-off-by: Tang Chen <tangchen@xxxxxxxxxxxxxx>
Signed-off-by: Miao Xie <miaox@xxxxxxxxxxxxxx>
---
arch/x86/kernel/cpu/mcheck/mce_intel.c | 30 +++++++++++++++++-------------
1 files changed, 17 insertions(+), 13 deletions(-)

diff --git a/arch/x86/kernel/cpu/mcheck/mce_intel.c b/arch/x86/kernel/cpu/mcheck/mce_intel.c
index 481d152..d8f0da6 100644
--- a/arch/x86/kernel/cpu/mcheck/mce_intel.c
+++ b/arch/x86/kernel/cpu/mcheck/mce_intel.c
@@ -163,34 +163,38 @@ void cmci_clear(void)
raw_spin_unlock_irqrestore(&cmci_discover_lock, flags);
}

+static long cmci_rediscover_work_func(void *arg)
+{
+ int banks;
+
+ /* Recheck banks in case CPUs don't all have the same */
+ if (cmci_supported(&banks))
+ cmci_discover(banks, 0);
+
+ return 0;
+}
+
/*
* After a CPU went down cycle through all the others and rediscover
* Must run in process context.
*/
void cmci_rediscover(int dying)
{
- int banks;
- int cpu;
- cpumask_var_t old;
+ int cpu, banks;

if (!cmci_supported(&banks))
return;
- if (!alloc_cpumask_var(&old, GFP_KERNEL))
- return;
- cpumask_copy(old, &current->cpus_allowed);

for_each_online_cpu(cpu) {
WARN_ON_ONCE(cpu == dying);

- if (set_cpus_allowed_ptr(current, cpumask_of(cpu)))
+ if (cpu == smp_processor_id()) {
+ cmci_rediscover_work_func(NULL);
continue;
- /* Recheck banks in case CPUs don't all have the same */
- if (cmci_supported(&banks))
- cmci_discover(banks, 0);
- }
+ }

- set_cpus_allowed_ptr(current, old);
- free_cpumask_var(old);
+ work_on_cpu(cpu, cmci_rediscover_work_func, NULL);
+ }
}

/*
--
1.7.1

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