ARM: bL_switcher: Allow detachment of outstanding switch requests

In rare situations, it may be neecssary to prevent a completer
registered using bL_switch_request_cb() from being called.

For example, a cpufreq driver module needs to ensure that its
completer won't get called if the module is about to be unloaded
from the kernel.

This patch provides a bL_switch_request_detach() function which
detaches the completer from an outstanding request.  The request
continues in the background, as if it had been started using
bL_switch_request().

If somebody else's completer is registered instead then the caller
shouldn't care about it, so nothing is done in this case.

Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>

1 files changed, 32 insertions, 0 deletions

diff --git a/arch/arm/common/bL_switcher.c b/arch/arm/common/bL_switcher.c
index 6fbc73b8e02..b9ee01717a8 100644
--- a/arch/arm/common/bL_switcher.c
+++ b/arch/arm/common/bL_switcher.c
@@ -386,6 +386,38 @@ int bL_switch_request_cb(unsigned int cpu, unsigned int new_cluster_id,
 EXPORT_SYMBOL_GPL(bL_switch_request_cb);
 
 /*
+ * Detach an outstanding switch request.
+ *
+ * The switcher will continue with the switch request in the background,
+ * but the completer function will not be called.
+ *
+ * This may be necessary if the completer is in a kernel module which is
+ * about to be unloaded.
+ */
+void bL_switch_request_detach(unsigned int cpu,
+			      bL_switch_completion_handler completer)
+{
+	struct bL_thread *t;
+
+	if (cpu >= ARRAY_SIZE(bL_threads)) {
+		pr_err("%s: cpu %d out of bounds\n", __func__, cpu);
+		return;
+	}
+
+	t = &bL_threads[cpu];
+
+	if (IS_ERR(t->task) || !t->task)
+		return;
+
+	spin_lock(&t->lock);
+	if (t->completer == completer)
+		t->completer = NULL;
+	spin_unlock(&t->lock);
+}
+
+EXPORT_SYMBOL_GPL(bL_switch_request_detach);
+
+/*
  * Activation and configuration code.
  */