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notifier: Fix broken error handling pattern

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The current notifiers have the following error handling pattern all
over the place:

	int err, nr;

	err = __foo_notifier_call_chain(&chain, val_up, v, -1, &nr);
	if (err & NOTIFIER_STOP_MASK)
		__foo_notifier_call_chain(&chain, val_down, v, nr-1, NULL)

And aside from the endless repetition thereof, it is broken. Consider
blocking notifiers; both calls take and drop the rwsem, this means
that the notifier list can change in between the two calls, making @nr
meaningless.

Fix this by replacing all the __foo_notifier_call_chain() functions
with foo_notifier_call_chain_robust() that embeds the above pattern,
but ensures it is inside a single lock region.

Note: I switched atomic_notifier_call_chain_robust() to use
      the spinlock, since RCU cannot provide the guarantee
      required for the recovery.

Note: software_resume() error handling was broken afaict.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/20200818135804.325626653@infradead.org
This commit is contained in:
Peter Zijlstra
2020-08-18 15:57:36 +02:00
committed by Ingo Molnar
parent f75aef392f
commit 70d9329857
9 changed files with 147 additions and 140 deletions
Download Patch File Download Diff File Expand all files Collapse all files

14
kernel/power/user.c
View File

@@ -46,7 +46,7 @@ int is_hibernate_resume_dev(const struct inode *bd_inode)
static int snapshot_open(struct inode *inode, struct file *filp)
{
struct snapshot_data *data;
int error, nr_calls = 0;
int error;
if (!hibernation_available())
return -EPERM;
@@ -73,9 +73,7 @@ static int snapshot_open(struct inode *inode, struct file *filp)
swap_type_of(swsusp_resume_device, 0, NULL) : -1;
data->mode = O_RDONLY;
data->free_bitmaps = false;
error = __pm_notifier_call_chain(PM_HIBERNATION_PREPARE, -1, &nr_calls);
if (error)
__pm_notifier_call_chain(PM_POST_HIBERNATION, --nr_calls, NULL);
error = pm_notifier_call_chain_robust(PM_HIBERNATION_PREPARE, PM_POST_HIBERNATION);
} else {
/*
* Resuming. We may need to wait for the image device to
@@ -85,15 +83,11 @@ static int snapshot_open(struct inode *inode, struct file *filp)
data->swap = -1;
data->mode = O_WRONLY;
error = __pm_notifier_call_chain(PM_RESTORE_PREPARE, -1, &nr_calls);
error = pm_notifier_call_chain_robust(PM_RESTORE_PREPARE, PM_POST_RESTORE);
if (!error) {
error = create_basic_memory_bitmaps();
data->free_bitmaps = !error;
} else
nr_calls--;
if (error)
__pm_notifier_call_chain(PM_POST_RESTORE, nr_calls, NULL);
}
}
if (error)
hibernate_release();