linux-kernel - [PATCH v3 2/6] freezer,umh: Clean up freezer/initrd interaction

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Date:   Mon, 22 Aug 2022 13:18:18 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     rjw@...ysocki.net, oleg@...hat.com, mingo@...nel.org,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, mgorman@...e.de, ebiederm@...ssion.com,
        bigeasy@...utronix.de, Will Deacon <will@...nel.org>
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org, tj@...nel.org,
        linux-pm@...r.kernel.org
Subject: [PATCH v3 2/6] freezer,umh: Clean up freezer/initrd interaction

handle_initrd() marks itself as PF_FREEZER_SKIP in order to ensure
that the UMH, which is going to freeze the system, doesn't
indefinitely wait for it's caller.

Rework things by adding UMH_FREEZABLE to indicate the completion is
freezable.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 include/linux/umh.h     |    9 +++++----
 init/do_mounts_initrd.c |   10 +---------
 kernel/umh.c            |    8 ++++++++
 3 files changed, 14 insertions(+), 13 deletions(-)

--- a/include/linux/umh.h
+++ b/include/linux/umh.h
@@ -11,10 +11,11 @@
 struct cred;
 struct file;
 
-#define UMH_NO_WAIT	0	/* don't wait at all */
-#define UMH_WAIT_EXEC	1	/* wait for the exec, but not the process */
-#define UMH_WAIT_PROC	2	/* wait for the process to complete */
-#define UMH_KILLABLE	4	/* wait for EXEC/PROC killable */
+#define UMH_NO_WAIT	0x00	/* don't wait at all */
+#define UMH_WAIT_EXEC	0x01	/* wait for the exec, but not the process */
+#define UMH_WAIT_PROC	0x02	/* wait for the process to complete */
+#define UMH_KILLABLE	0x04	/* wait for EXEC/PROC killable */
+#define UMH_FREEZABLE	0x08	/* wait for EXEC/PROC freezable */
 
 struct subprocess_info {
 	struct work_struct work;
--- a/init/do_mounts_initrd.c
+++ b/init/do_mounts_initrd.c
@@ -79,19 +79,11 @@ static void __init handle_initrd(void)
 	init_mkdir("/old", 0700);
 	init_chdir("/old");
 
-	/*
-	 * In case that a resume from disk is carried out by linuxrc or one of
-	 * its children, we need to tell the freezer not to wait for us.
-	 */
-	current->flags |= PF_FREEZER_SKIP;
-
 	info = call_usermodehelper_setup("/linuxrc", argv, envp_init,
 					 GFP_KERNEL, init_linuxrc, NULL, NULL);
 	if (!info)
 		return;
-	call_usermodehelper_exec(info, UMH_WAIT_PROC);
-
-	current->flags &= ~PF_FREEZER_SKIP;
+	call_usermodehelper_exec(info, UMH_WAIT_PROC|UMH_FREEZABLE);
 
 	/* move initrd to rootfs' /old */
 	init_mount("..", ".", NULL, MS_MOVE, NULL);
--- a/kernel/umh.c
+++ b/kernel/umh.c
@@ -28,6 +28,7 @@
 #include <linux/async.h>
 #include <linux/uaccess.h>
 #include <linux/initrd.h>
+#include <linux/freezer.h>
 
 #include <trace/events/module.h>
 
@@ -436,6 +437,9 @@ int call_usermodehelper_exec(struct subp
 	if (wait == UMH_NO_WAIT)	/* task has freed sub_info */
 		goto unlock;
 
+	if (wait & UMH_FREEZABLE)
+		freezer_do_not_count();
+
 	if (wait & UMH_KILLABLE) {
 		retval = wait_for_completion_killable(&done);
 		if (!retval)
@@ -448,6 +452,10 @@ int call_usermodehelper_exec(struct subp
 	}
 
 	wait_for_completion(&done);
+
+	if (wait & UMH_FREEZABLE)
+		freezer_count();
+
 wait_done:
 	retval = sub_info->retval;
 out: