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Subject[PATCH] i386 adds smp_call_function_single
Hello,

Continiung the series of small patches necessary for the perfmon subsystem, here
is a patch that adds support for the smp_call_function_single() function for i386.
It exists for almost all other architectures but i386. The perfmon subsystem
needs it in one case to free some state on a designated remote CPU.

Changelog:
- adds smp_call_function_single() to i386 tree. This function
is used to invoked a procedure on a designated remote CPU.

<signed-off-by>: eranian@hpl.hp.com

diff --git a/arch/i386/kernel/smp.c b/arch/i386/kernel/smp.c
--- a/arch/i386/kernel/smp.c
+++ b/arch/i386/kernel/smp.c
@@ -634,3 +634,69 @@ fastcall void smp_call_function_interrup
}
}

+/*
+ * this function sends a 'generic call function' IPI to one other CPU
+ * in the system.
+ *
+ * cpu is a standard Linux logical CPU number.
+ */
+static void
+__smp_call_function_single(int cpu, void (*func) (void *info), void *info,
+ int nonatomic, int wait)
+{
+ struct call_data_struct data;
+ int cpus = 1;
+
+ data.func = func;
+ data.info = info;
+ atomic_set(&data.started, 0);
+ data.wait = wait;
+ if (wait)
+ atomic_set(&data.finished, 0);
+
+ call_data = &data;
+ wmb();
+ /* Send a message to all other CPUs and wait for them to respond */
+ send_IPI_mask(cpumask_of_cpu(cpu), CALL_FUNCTION_VECTOR);
+
+ /* Wait for response */
+ while (atomic_read(&data.started) != cpus)
+ cpu_relax();
+
+ if (!wait)
+ return;
+
+ while (atomic_read(&data.finished) != cpus)
+ cpu_relax();
+}
+
+/*
+ * smp_call_function_single - Run a function on another CPU
+ * @func: The function to run. This must be fast and non-blocking.
+ * @info: An arbitrary pointer to pass to the function.
+ * @nonatomic: Currently unused.
+ * @wait: If true, wait until function has completed on other CPUs.
+ *
+ * Retrurns 0 on success, else a negative status code.
+ *
+ * Does not return until the remote CPU is nearly ready to execute <func>
+ * or is or has executed.
+ */
+
+int smp_call_function_single (int cpu, void (*func) (void *info), void *info,
+ int nonatomic, int wait)
+{
+ /* prevent preemption and reschedule on another processor */
+ int me = get_cpu();
+ if (cpu == me) {
+ WARN_ON(1);
+ put_cpu();
+ return -EBUSY;
+ }
+ spin_lock_bh(&call_lock);
+ __smp_call_function_single(cpu, func, info, nonatomic, wait);
+ spin_unlock_bh(&call_lock);
+ put_cpu();
+ return 0;
+}
+EXPORT_SYMBOL(smp_call_function_single);
-
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