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Message-ID: <555101fd-71bc-fa0b-98c2-69249bb3eda6@huawei.com>
Date: Fri, 15 May 2020 13:38:38 +0100
From: John Garry <john.garry@...wei.com>
To: Kai-Heng Feng <kai.heng.feng@...onical.com>, <axboe@...nel.dk>
CC: "open list:LIBATA SUBSYSTEM (Serial and Parallel ATA drivers)"
<linux-ide@...r.kernel.org>,
open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] libata: Use per port sync for detach
On 15/05/2020 12:09, 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.
It would be nice to describe this circular dependency a bit more.
>
> 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.
oh, I thought that we could avoid the hassle of per-port cookie
management. Sorry.
Did you check if the original issue which I tried to remedy is still
suppressed?
I tried your patch, and got this:
[ 28.190587] ------------[ cut here ]------------
[ 28.195194] WARNING: CPU: 79 PID: 1 at drivers/ata/libata-core.c:5888
ata_hos
t_detach+0x238/0x248
[ 28.204025] Modules linked in:
[ 28.207072] CPU: 79 PID: 1 Comm: swapper/0 Tainted: G W
5.7.0-
rc5-g644cd6f-dirty #84
[ 28.216076] Hardware name: Huawei TaiShan 2280 V2/BC82AMDC, BIOS
2280-V2 CS V
3.B220.02 03/27/2020
[ 28.224906] pstate: 20c00009 (nzCv daif +PAN +UAO)
[ 28.229677] pc : ata_host_detach+0x238/0x248
[ 28.233929] lr : ata_host_detach+0x12c/0x248
[ 28.238181] sp : ffff0026dc74f980
[ 28.241481] x29: ffff0026dc74f980 x28: 0000000000000000
[ 28.246769] x27: ffff2026c541c010 x26: 00000000000038e0
[ 28.252059] x25: 0000000000003590 x24: ffff0026d3a0a018
[ 28.257350] x23: 0000000000000001 x22: ffff0026d3a0a000
[ 28.262638] x21: 0000000000013ec0 x20: ffff2026c541c000
[ 28.267928] x19: ffff2026c541c020 x18: 0000000000000000
[ 28.273215] x17: 0000000000000000 x16: 0000000000000000
[ 28.278504] x15: 00000000000006c0 x14: 0000000000000000
[ 28.283792] x13: 0000000000000000 x12: 1fffe004da744317
[ 28.289081] x11: ffff8004da744317 x10: dfffa00000000000
[ 28.294370] x9 : ffff8004da744318 x8 : ffff0026d3a218bc
[ 28.299657] x7 : 0000000000000001 x6 : ffff8004da744318
[ 28.304945] x5 : ffff8004da744318 x4 : dfffa00000000000
[ 28.310233] x3 : ffffa00075ea18b4 x2 : 0000000000000003
[ 28.315521] x1 : 0000000000000000 x0 : 0000000000400200
[ 28.320808] Call trace:
[ 28.323246] ata_host_detach+0x238/0x248
[ 28.327153] ata_pci_remove_one+0x24/0x38
[ 28.331147] ahci_remove_one+0x54/0x88
[ 28.334881] pci_device_remove+0x70/0x148
[ 28.338874] really_probe+0x17c/0x570
[ 28.342522] driver_probe_device+0x80/0x150
[ 28.346690] device_driver_attach+0x9c/0xa8
[ 28.350856] __driver_attach+0xac/0x118
[ 28.354677] bus_for_each_dev+0xf0/0x168
[ 28.358584] driver_attach+0x34/0x48
[ 28.362146] bus_add_driver+0x240/0x300
[ 28.365966] driver_register+0xc0/0x1e0
[ 28.369787] __pci_register_driver+0xb4/0xd0
[ 28.374039] ahci_pci_driver_init+0x24/0x30
[ 28.378205] do_one_initcall+0xb8/0x268
[ 28.382027] kernel_init_freeable+0x294/0x30c
[ 28.386366] kernel_init+0x14/0x120
[ 28.389841] ret_from_fork+0x10/0x1c
[ 28.393400] ---[ end trace 9972785c7052048f ]---
[ 28.435826] ahci 0000:b4:03.0: SSS flag set, parallel bus scan disabled
Thanks,
John
>
> Fixes: 130f4caf145c ("libata: Ensure ata_port probe has completed before detach")
> BugLink: https://bugs.launchpad.net/bugs/1867983
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
> ---
> drivers/ata/libata-core.c | 6 +++---
> include/linux/libata.h | 3 +++
> 2 files changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
> index beca5f91bb4c..4a698f6388cd 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;
> @@ -5921,7 +5920,8 @@ void ata_host_detach(struct ata_host *host)
> int i;
>
> /* Ensure ata_port probe has completed */
> - async_synchronize_full();
> + for (i = 0; i < host->n_ports; i++)
> + async_synchronize_cookie(host->ports[i]->cookie);
>
> for (i = 0; i < host->n_ports; i++)
Is it possible to combine these "for" loops?
> ata_port_detach(host->ports[i]);
> 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>
>
alphabetic?
> /*
> * 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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