linux-kernel - [PATCH] dd: Invoke one probe retry cycle after every initcall level

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Date:   Thu, 19 Jul 2018 14:24:00 -0700
From:   Rishabh Bhatnagar <rishabhb@...eaurora.org>
To:     gregkh@...uxfoundation.org
Cc:     linux-kernel@...r.kernel.org, ckadabi@...eaurora.org,
        tsoni@...eaurora.org, Rishabh Bhatnagar <rishabhb@...eaurora.org>,
        Vikram Mulukutla <markivx@...eaurora.org>
Subject: [PATCH] dd: Invoke one probe retry cycle after every initcall level

Drivers that are registered at an initcall level may have to
wait until late_init before the probe deferral mechanism can
retry their probe functions. It is possible that their
dependencies were resolved much earlier, in some cases even
before the next initcall level. Invoke one probe retry cycle
at every _sync initcall level, allowing these drivers to be
probed earlier.

Signed-off-by: Vikram Mulukutla <markivx@...eaurora.org>
Signed-off-by: Rishabh Bhatnagar <rishabhb@...eaurora.org>
---
 drivers/base/dd.c | 33 +++++++++++++++++++++++++++------
 1 file changed, 27 insertions(+), 6 deletions(-)

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 1435d72..e6a6821 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -224,23 +224,44 @@ void device_unblock_probing(void)
 	driver_deferred_probe_trigger();
 }
 
+static void enable_trigger_defer_cycle(void)
+{
+	driver_deferred_probe_enable = true;
+	driver_deferred_probe_trigger();
+	/*
+	 * Sort as many dependencies as possible before the next initcall
+	 * level
+	 */
+	flush_work(&deferred_probe_work);
+}
+
 /**
  * deferred_probe_initcall() - Enable probing of deferred devices
  *
  * We don't want to get in the way when the bulk of drivers are getting probed.
  * Instead, this initcall makes sure that deferred probing is delayed until
- * late_initcall time.
+ * all the registered initcall functions at a particular level are completed.
+ * This function is invoked at every *_initcall_sync level.
  */
 static int deferred_probe_initcall(void)
 {
-	driver_deferred_probe_enable = true;
-	driver_deferred_probe_trigger();
-	/* Sort as many dependencies as possible before exiting initcalls */
-	flush_work(&deferred_probe_work);
+	enable_trigger_defer_cycle();
+	driver_deferred_probe_enable = false;
+	return 0;
+}
+arch_initcall_sync(deferred_probe_initcall);
+subsys_initcall_sync(deferred_probe_initcall);
+fs_initcall_sync(deferred_probe_initcall);
+device_initcall_sync(deferred_probe_initcall);
+
+static int deferred_probe_enable_fn(void)
+{
+	/* Enable deferred probing for all time */
+	enable_trigger_defer_cycle();
 	initcalls_done = true;
 	return 0;
 }
-late_initcall(deferred_probe_initcall);
+late_initcall(deferred_probe_enable_fn);
 
 /**
  * device_is_bound() - Check if device is bound to a driver
-- 
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