From 38f087de8947700d3b06d3d1594490e0f611c5d1 Mon Sep 17 00:00:00 2001 From: Rasmus Villemoes Date: Fri, 12 Mar 2021 11:30:26 +0100 Subject: devtmpfs: fix placement of complete() call Calling complete() from within the __init function is wrong - theoretically, the init process could proceed all the way to freeing the init mem before the devtmpfsd thread gets to execute the return instruction in devtmpfs_setup(). In practice, it seems to be harmless as gcc inlines devtmpfs_setup() into devtmpfsd(). So the calls of the __init functions init_chdir() etc. actually happen from devtmpfs_setup(), but the __ref on that one silences modpost (it's all right, because those calls happen before the complete()). But it does make the __init annotation of the setup function moot, which we'll fix in a subsequent patch. Fixes: bcbacc4909f1 ("devtmpfs: refactor devtmpfsd()") Reviewed-by: Christoph Hellwig Signed-off-by: Rasmus Villemoes Link: https://lore.kernel.org/r/20210312103027.2701413-1-linux@rasmusvillemoes.dk Signed-off-by: Greg Kroah-Hartman --- drivers/base/devtmpfs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/base/devtmpfs.c') diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c index 653c8c6ac7a7..aedeb2dc1a18 100644 --- a/drivers/base/devtmpfs.c +++ b/drivers/base/devtmpfs.c @@ -419,7 +419,6 @@ static int __init devtmpfs_setup(void *p) init_chroot("."); out: *(int *)p = err; - complete(&setup_done); return err; } @@ -432,6 +431,7 @@ static int __ref devtmpfsd(void *p) { int err = devtmpfs_setup(p); + complete(&setup_done); if (err) return err; devtmpfs_work_loop(); -- cgit v1.2.3 From 01085e24ff0ae775e7407a6e40c2156a724ae884 Mon Sep 17 00:00:00 2001 From: Rasmus Villemoes Date: Fri, 12 Mar 2021 11:30:27 +0100 Subject: devtmpfs: actually reclaim some init memory Currently gcc seems to inline devtmpfs_setup() into devtmpfsd(), so its memory footprint isn't reclaimed as intended. Mark it noinline to make sure it gets put in .init.text. While here, setup_done can also be put in .init.data: After complete() releases the internal spinlock, the completion object is never touched again by that thread, and the waiting thread doesn't proceed until it observes ->done while holding that spinlock. This is now the same pattern as for kthreadd_done in init/main.c: complete() is done in a __ref function, while the corresponding wait_for_completion() is in an __init function. Reviewed-by: Christoph Hellwig Signed-off-by: Rasmus Villemoes Link: https://lore.kernel.org/r/20210312103027.2701413-2-linux@rasmusvillemoes.dk Signed-off-by: Greg Kroah-Hartman --- drivers/base/devtmpfs.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'drivers/base/devtmpfs.c') diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c index aedeb2dc1a18..8be352ab4ddb 100644 --- a/drivers/base/devtmpfs.c +++ b/drivers/base/devtmpfs.c @@ -371,7 +371,7 @@ int __init devtmpfs_mount(void) return err; } -static DECLARE_COMPLETION(setup_done); +static __initdata DECLARE_COMPLETION(setup_done); static int handle(const char *name, umode_t mode, kuid_t uid, kgid_t gid, struct device *dev) @@ -405,7 +405,7 @@ static void __noreturn devtmpfs_work_loop(void) } } -static int __init devtmpfs_setup(void *p) +static noinline int __init devtmpfs_setup(void *p) { int err; -- cgit v1.2.3