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SubjectRe: [PATCH v2] libata: Use per port sync for detach
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On 21/05/2020 05:30, Kai-Heng Feng wrote:
> Commit 130f4caf145c ("libata: Ensure ata_port probe has completed before
> detach") may cause system freeze during suspend.
>
> Using async_synchronize_full() in PM callbacks is wrong, since async
> callbacks that are already scheduled may wait for not-yet-scheduled
> callbacks, causes a circular dependency.
>
> Instead of using big hammer like async_synchronize_full(), use async
> cookie to make sure port probe are synced, without affecting other
> scheduled PM callbacks.
>

Apart from nit, it looks ok.

Cheers,
John

> Fixes: 130f4caf145c ("libata: Ensure ata_port probe has completed before detach")
> BugLink: https://bugs.launchpad.net/bugs/1867983
> Suggested-by: John Garry <john.garry@huawei.com>
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
> ---
> v2:
> - Sync up to cookie + 1.
> - Squash the synchronization into the same loop.
>
> drivers/ata/libata-core.c | 9 ++++-----
> include/linux/libata.h | 3 +++
> 2 files changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
> index beca5f91bb4c..b6be84f2cecb 100644
> --- a/drivers/ata/libata-core.c
> +++ b/drivers/ata/libata-core.c
> @@ -42,7 +42,6 @@
> #include <linux/workqueue.h>
> #include <linux/scatterlist.h>
> #include <linux/io.h>
> -#include <linux/async.h>
> #include <linux/log2.h>
> #include <linux/slab.h>
> #include <linux/glob.h>
> @@ -5778,7 +5777,7 @@ int ata_host_register(struct ata_host *host, struct scsi_host_template *sht)
> /* perform each probe asynchronously */
> for (i = 0; i < host->n_ports; i++) {
> struct ata_port *ap = host->ports[i];
> - async_schedule(async_port_probe, ap);
> + ap->cookie = async_schedule(async_port_probe, ap);
> }
>
> return 0;
> @@ -5921,10 +5920,10 @@ void ata_host_detach(struct ata_host *host)
> int i;
>
> /* Ensure ata_port probe has completed */

nit: maybe we can relocate this comment

> - async_synchronize_full();
> -
> - for (i = 0; i < host->n_ports; i++)
> + for (i = 0; i < host->n_ports; i++) {
> + async_synchronize_cookie(host->ports[i]->cookie + 1);
> ata_port_detach(host->ports[i]);
> + }
>
> /* the host is dead now, dissociate ACPI */
> ata_acpi_dissociate(host);
> diff --git a/include/linux/libata.h b/include/linux/libata.h
> index cffa4714bfa8..ae6dfc107ea8 100644
> --- a/include/linux/libata.h
> +++ b/include/linux/libata.h
> @@ -22,6 +22,7 @@
> #include <linux/acpi.h>
> #include <linux/cdrom.h>
> #include <linux/sched.h>
> +#include <linux/async.h>
>
> /*
> * Define if arch has non-standard setup. This is a _PCI_ standard
> @@ -872,6 +873,8 @@ struct ata_port {
> struct timer_list fastdrain_timer;
> unsigned long fastdrain_cnt;
>
> + async_cookie_t cookie;
> +
> int em_message_type;
> void *private_data;
>
>

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