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Subject[PATCH] x86, apm: Make on_cpu0() use workqueue instead of work_on_cpu()
Make APM schedule a work item on CPU0 instead of using the expensive
work_on_cpu(); hopefully, this is the last user of work_on_cpu() and
we can take out work_on_cpu() in not too distant future.

Tested both paths. Seems to work fine.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
arch/x86/kernel/apm_32.c | 31 +++++++++++++++++++++++--------
1 file changed, 23 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/apm_32.c b/arch/x86/kernel/apm_32.c
index d65464e..2bdb8c4 100644
--- a/arch/x86/kernel/apm_32.c
+++ b/arch/x86/kernel/apm_32.c
@@ -605,28 +605,43 @@ static long __apm_bios_call(void *_call)
return call->eax & 0xff;
}

+struct on_cpu0_arg {
+ struct work_struct work;
+ long (*fn)(void *);
+ struct apm_bios_call *call;
+ int ret;
+};
+
+static void on_cpu0_workfn(struct work_struct *work)
+{
+ struct on_cpu0_arg *arg = container_of(work, struct on_cpu0_arg, work);
+
+ arg->ret = arg->fn(arg->call);
+}
+
/* Run __apm_bios_call or __apm_bios_call_simple on CPU 0 */
static int on_cpu0(long (*fn)(void *), struct apm_bios_call *call)
{
- int ret;
+ struct on_cpu0_arg arg = { .fn = fn, .call = call };

- /* Don't bother with work_on_cpu in the common case, so we don't
- * have to worry about OOM or overhead. */
+ /* directly invoke on_cpu0_workfn() in the common case */
if (get_cpu() == 0) {
- ret = fn(call);
+ on_cpu0_workfn(&arg.work);
put_cpu();
} else {
put_cpu();
- ret = work_on_cpu(0, fn, call);
+ INIT_WORK_ONSTACK(&arg.work, on_cpu0_workfn);
+ schedule_work_on(0, &arg.work);
+ flush_work(&arg.work);
}

/* work_on_cpu can fail with -ENOMEM */
- if (ret < 0)
- call->err = ret;
+ if (arg.ret < 0)
+ call->err = arg.ret;
else
call->err = (call->eax >> 8) & 0xff;

- return ret;
+ return arg.ret;
}

/**

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