| Message ID | 20211009101444.912374035@infradead.org (mailing list archive) |
|---|---|
| State | Deferred, archived |
| Headers | show |
| Series | Freezer rewrite | expand |
On Sat, Oct 09, 2021 at 12:07:56PM +0200, Peter Zijlstra wrote: > 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@infradead.org> > --- > include/linux/umh.h | 9 +++++---- > init/do_mounts_initrd.c | 10 +--------- > kernel/umh.c | 8 ++++++++ > 3 files changed, 14 insertions(+), 13 deletions(-) This looks much better to me: Acked-by: Will Deacon <will@kernel.org> Just a question on the old code: > --- 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; How was this supposed to work if it raced with the freezer checking the flag? Will
--- 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:
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@infradead.org> --- include/linux/umh.h | 9 +++++---- init/do_mounts_initrd.c | 10 +--------- kernel/umh.c | 8 ++++++++ 3 files changed, 14 insertions(+), 13 deletions(-)