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Message-ID: <CAJZ5v0jrj3PaC5oZt22DQoJARUcpXaerS-Cmx+34du7=p9WDSw@mail.gmail.com>
Date: Tue, 23 May 2023 20:33:44 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Christoph Hellwig <hch@....de>
Cc: Jens Axboe <axboe@...nel.dk>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"Rafael J. Wysocki" <rafael@...nel.org>,
Mike Snitzer <snitzer@...nel.org>,
Joern Engel <joern@...ybastard.org>,
Miquel Raynal <miquel.raynal@...tlin.com>,
Richard Weinberger <richard@....at>,
Vignesh Raghavendra <vigneshr@...com>,
Pavel Machek <pavel@....cz>, dm-devel@...hat.com,
linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
linux-mtd@...ts.infradead.org, linux-pm@...r.kernel.org
Subject: Re: [PATCH 04/24] PM: hibernate: move finding the resume device out
of software_resume
On Tue, May 23, 2023 at 9:45 AM Christoph Hellwig <hch@....de> wrote:
>
> software_resume can be called either from an init call in the boot code,
> or from sysfs once the system has finished booting, and the two
> invocation methods this can't race with each other.
>
> For the latter case we did just parse the suspend device manually, while
> the former might not have one. Split software_resume so that the search
> only happens for the boot case, which also means the special lockdep
> nesting annotation can go away as the system transition mutex can be
> taken a little later and doesn't have the sysfs locking nest inside it.
>
> Signed-off-by: Christoph Hellwig <hch@....de>
Acked-by: Rafael J. Wysocki <rafael@...nel.org>
> ---
> kernel/power/hibernate.c | 80 ++++++++++++++++++++--------------------
> 1 file changed, 39 insertions(+), 41 deletions(-)
>
> diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
> index 78696aa04f5ca3..45e24b02cd50b6 100644
> --- a/kernel/power/hibernate.c
> +++ b/kernel/power/hibernate.c
> @@ -907,7 +907,7 @@ int hibernate_quiet_exec(int (*func)(void *data), void *data)
> }
> EXPORT_SYMBOL_GPL(hibernate_quiet_exec);
>
> -static int find_resume_device(void)
> +static int __init find_resume_device(void)
> {
> if (!strlen(resume_file))
> return -ENOENT;
> @@ -942,53 +942,16 @@ static int find_resume_device(void)
> return 0;
> }
>
> -/**
> - * software_resume - Resume from a saved hibernation image.
> - *
> - * This routine is called as a late initcall, when all devices have been
> - * discovered and initialized already.
> - *
> - * The image reading code is called to see if there is a hibernation image
> - * available for reading. If that is the case, devices are quiesced and the
> - * contents of memory is restored from the saved image.
> - *
> - * If this is successful, control reappears in the restored target kernel in
> - * hibernation_snapshot() which returns to hibernate(). Otherwise, the routine
> - * attempts to recover gracefully and make the kernel return to the normal mode
> - * of operation.
> - */
> static int software_resume(void)
> {
> int error;
>
> - /*
> - * If the user said "noresume".. bail out early.
> - */
> - if (noresume || !hibernation_available())
> - return 0;
> -
> - /*
> - * name_to_dev_t() below takes a sysfs buffer mutex when sysfs
> - * is configured into the kernel. Since the regular hibernate
> - * trigger path is via sysfs which takes a buffer mutex before
> - * calling hibernate functions (which take system_transition_mutex)
> - * this can cause lockdep to complain about a possible ABBA deadlock
> - * which cannot happen since we're in the boot code here and
> - * sysfs can't be invoked yet. Therefore, we use a subclass
> - * here to avoid lockdep complaining.
> - */
> - mutex_lock_nested(&system_transition_mutex, SINGLE_DEPTH_NESTING);
> -
> - if (!swsusp_resume_device) {
> - error = find_resume_device();
> - if (error)
> - goto Unlock;
> - }
> -
> pm_pr_dbg("Hibernation image partition %d:%d present\n",
> MAJOR(swsusp_resume_device), MINOR(swsusp_resume_device));
>
> pm_pr_dbg("Looking for hibernation image.\n");
> +
> + mutex_lock(&system_transition_mutex);
> error = swsusp_check(false);
> if (error)
> goto Unlock;
> @@ -1035,7 +998,39 @@ static int software_resume(void)
> goto Finish;
> }
>
> -late_initcall_sync(software_resume);
> +/**
> + * software_resume_initcall - Resume from a saved hibernation image.
> + *
> + * This routine is called as a late initcall, when all devices have been
> + * discovered and initialized already.
> + *
> + * The image reading code is called to see if there is a hibernation image
> + * available for reading. If that is the case, devices are quiesced and the
> + * contents of memory is restored from the saved image.
> + *
> + * If this is successful, control reappears in the restored target kernel in
> + * hibernation_snapshot() which returns to hibernate(). Otherwise, the routine
> + * attempts to recover gracefully and make the kernel return to the normal mode
> + * of operation.
> + */
> +static int __init software_resume_initcall(void)
> +{
> + /*
> + * If the user said "noresume".. bail out early.
> + */
> + if (noresume || !hibernation_available())
> + return 0;
> +
> + if (!swsusp_resume_device) {
> + int error = find_resume_device();
> +
> + if (error)
> + return error;
> + }
> +
> + return software_resume();
> +}
> +late_initcall_sync(software_resume_initcall);
>
>
> static const char * const hibernation_modes[] = {
> @@ -1176,6 +1171,9 @@ static ssize_t resume_store(struct kobject *kobj, struct kobj_attribute *attr,
> char *name;
> dev_t res;
>
> + if (!hibernation_available())
> + return 0;
> +
> if (len && buf[len-1] == '\n')
> len--;
> name = kstrndup(buf, len, GFP_KERNEL);
> --
> 2.39.2
>
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