power/suspend: Add delay for device quirks

Author: qzed

kernel/power/suspend.c

@@ -533,6 +533,8 @@ int suspend_devices_and_enter(suspend_state_t state)
 	goto Resume_devices;
 }
 
+unsigned int resume_delay = 3000;
+
 /**
  * suspend_finish - Clean up before finishing the suspend sequence.
  *
@@ -541,6 +543,15 @@ int suspend_devices_and_enter(suspend_state_t state)
  */
 static void suspend_finish(void)
 {
+	if (resume_delay) {
+		/* Give kernel threads a head start, such that usb-storage
+		 * can detect devices before syslog attempts to write log
+		 * messages from the suspend code.
+		 */
+		thaw_kernel_threads();
+		pr_debug("PM: Sleeping for %d milliseconds.\n", resume_delay);
+		msleep(resume_delay);
+	}
 	suspend_thaw_processes();
 	pm_notifier_call_chain(PM_POST_SUSPEND);
 	pm_restore_console();

kernel/sysctl.c

@@ -315,7 +315,16 @@ static int min_extfrag_threshold;
 static int max_extfrag_threshold = 1000;
 #endif
 
+extern unsigned int resume_delay;
+
 static struct ctl_table kern_table[] = {
+	{
+		.procname	= "resume_delay",
+		.data		= &resume_delay,
+		.maxlen		= sizeof(unsigned int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
 	{
 		.procname	= "sched_child_runs_first",
 		.data		= &sysctl_sched_child_runs_first,