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Niklas Cassel f6cf19c1b3 ata: libata-eh: do not clear ATA_PFLAG_EH_PENDING in ata_eh_reset() 
[ Upstream commit 80cc944eca4f0baa9c381d0706f3160e491437f2 ]

ata_scsi_port_error_handler() starts off by clearing ATA_PFLAG_EH_PENDING,
before calling ap->ops->error_handler() (without holding the ap->lock).

If an error IRQ is received while ap->ops->error_handler() is running,
the irq handler will set ATA_PFLAG_EH_PENDING.

Once ap->ops->error_handler() returns, ata_scsi_port_error_handler()
checks if ATA_PFLAG_EH_PENDING is set, and if it is, another iteration
of ATA EH is performed.

The problem is that ATA_PFLAG_EH_PENDING is not only cleared by
ata_scsi_port_error_handler(), it is also cleared by ata_eh_reset().

ata_eh_reset() is called by ap->ops->error_handler(). This additional
clearing done by ata_eh_reset() breaks the whole retry logic in
ata_scsi_port_error_handler(). Thus, if an error IRQ is received while
ap->ops->error_handler() is running, the port will currently remain
frozen and will never get re-enabled.

The additional clearing in ata_eh_reset() was introduced in commit
1e641060c4 ("libata: clear eh_info on reset completion").

Looking at the original error report:
https://marc.info/?l=linux-ide&m=124765325828495&w=2

We can see the following happening:
[    1.074659] ata3: XXX port freeze
[    1.074700] ata3: XXX hardresetting link, stopping engine
[    1.074746] ata3: XXX flipping SControl

[    1.411471] ata3: XXX irq_stat=400040 CONN|PHY
[    1.411475] ata3: XXX port freeze

[    1.420049] ata3: XXX starting engine
[    1.420096] ata3: XXX rc=0, class=1
[    1.420142] ata3: XXX clearing IRQs for thawing
[    1.420188] ata3: XXX port thawed
[    1.420234] ata3: SATA link up 3.0 Gbps (SStatus 123 SControl 300)

We are not supposed to be able to receive an error IRQ while the port is
frozen (PxIE is set to 0, i.e. all IRQs for the port are disabled).

AHCI 1.3.1 section 10.7.1.1 First Tier (IS Register) states:
"Each bit location can be thought of as reporting a '1' if the virtual
"interrupt line" for that port is indicating it wishes to generate an
interrupt. That is, if a port has one or more interrupt status bit set,
and the enables for those status bits are set, then this bit shall be set."

Additionally, AHCI state P:ComInit clearly shows that the state machine
will only jump to P:ComInitSetIS (which sets IS.IPS(x) to '1'), if PxIE.PCE
is set to '1'. In our case, PxIE is set to 0, so IS.IPS(x) won't get set.

So IS.IPS(x) only gets set if PxIS and PxIE is set.

AHCI 1.3.1 section 10.7.1.1 First Tier (IS Register) also states:
"The bits in this register are read/write clear. It is set by the level of
the virtual interrupt line being a set, and cleared by a write of '1' from
the software."

So if IS.IPS(x) is set, you need to explicitly clear it by writing a 1 to
IS.IPS(x) for that port.

Since PxIE is cleared, the only way to get an interrupt while the port is
frozen, is if IS.IPS(x) is set, and the only way IS.IPS(x) can be set when
the port is frozen, is if it was set before the port was frozen.

However, since commit 737dd811a3db ("ata: libahci: clear pending interrupt
status"), we clear both PxIS and IS.IPS(x) after freezing the port, but
before the COMRESET, so the problem that commit 1e641060c4 ("libata:
clear eh_info on reset completion") fixed can no longer happen.

Thus, revert commit 1e641060c4 ("libata: clear eh_info on reset
completion"), so that the retry logic in ata_scsi_port_error_handler()
works once again. (The retry logic is still needed, since we can still
get an error IRQ _after_ the port has been thawed, but before
ata_scsi_port_error_handler() takes the ap->lock in order to check
if ATA_PFLAG_EH_PENDING is set.)

Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2023-10-10 21:53:32 +02:00
arch parisc: irq: Make irq_stack_union static to avoid sparse warning 2023-10-10 21:53:32 +02:00
block block/partition: fix signedness issue for Amiga partitions 2023-07-27 08:44:18 +02:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:13:17 +02:00
crypto crypto: lrw,xts - Replace strlcpy with strscpy 2023-09-23 11:01:05 +02:00
Documentation perf/smmuv3: Enable HiSilicon Erratum 162001900 quirk for HIP08/09 2023-09-23 11:01:05 +02:00
drivers ata: libata-eh: do not clear ATA_PFLAG_EH_PENDING in ata_eh_reset() 2023-10-10 21:53:32 +02:00
fs btrfs: reset destination buffer when read_extent_buffer() gets invalid range 2023-10-10 21:53:30 +02:00
include ata: libata: Rename link flag ATA_LFLAG_NO_DB_DELAY 2023-10-10 21:53:30 +02:00
init x86/mm: Initialize text poking earlier 2023-08-08 19:57:39 +02:00
io_uring io_uring: break iopolling on signal 2023-09-19 12:20:24 +02:00
ipc ipc/sem: Fix dangling sem_array access in semtimedop race 2022-12-08 11:24:00 +01:00
kernel ring-buffer: Do not attempt to read past "commit" 2023-10-10 21:53:32 +02:00
lib kobject: Add sanity check for kset->kobj.ktype in kset_register() 2023-09-23 11:01:08 +02:00
LICENSES LICENSES/deprecated: add Zlib license text 2020-09-16 14:33:49 +02:00
mm mm/filemap: fix infinite loop in generic_file_buffered_read() 2023-09-23 11:01:10 +02:00
net netfilter: nft_exthdr: Fix non-linear header modification 2023-10-10 21:53:30 +02:00
samples samples/hw_breakpoint: fix building without module unloading 2023-09-23 11:01:09 +02:00
scripts kconfig: fix possible buffer overflow 2023-09-19 12:20:25 +02:00
security smackfs: Prevent underflow in smk_set_cipso() 2023-09-19 12:20:13 +02:00
sound ASoC: imx-audmix: Fix return error with devm_clk_get() 2023-10-10 21:53:27 +02:00
tools selftests: fix dependency checker script 2023-10-10 21:53:32 +02:00
usr usr/include/Makefile: add linux/nfc.h to the compile-test coverage 2022-02-01 17:25:48 +01:00
virt KVM: fix memoryleak in kvm_init() 2023-04-05 11:23:43 +02:00
.clang-format RDMA 5.10 pull request 2020-10-17 11:18:18 -07:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore kbuild: generate Module.symvers only when vmlinux exists 2021-05-19 10:12:59 +02:00
.mailmap mailmap: add two more addresses of Uwe Kleine-König 2020-12-06 10:19:07 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Jason Cooper to CREDITS 2020-11-30 10:20:34 +01:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Remove DECnet support from kernel 2023-06-21 15:45:38 +02:00
Makefile Linux 5.10.197 2023-09-23 11:01:11 +02:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.