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Bart Van Assche 2d8b9f991d scsi: ide: Do not set the RQF_PREEMPT flag for sense requests 
[ Upstream commit 96d86e6a80 ]

RQF_PREEMPT is used for two different purposes in the legacy IDE code:

 1. To mark power management requests.

 2. To mark requests that should preempt another request. An (old)
    explanation of that feature is as follows: "The IDE driver in the Linux
    kernel normally uses a series of busywait delays during its
    initialization. When the driver executes these busywaits, the kernel
    does nothing for the duration of the wait. The time spent in these
    waits could be used for other initialization activities, if they could
    be run concurrently with these waits.

    More specifically, busywait-style delays such as udelay() in module
    init functions inhibit kernel preemption because the Big Kernel Lock is
    held, while yielding APIs such as schedule_timeout() allow
    preemption. This is true because the kernel handles the BKL specially
    and releases and reacquires it across reschedules allowed by the
    current thread.

    This IDE-preempt specification requires that the driver eliminate these
    busywaits and replace them with a mechanism that allows other work to
    proceed while the IDE driver is initializing."

Since I haven't found an implementation of (2), do not set the PREEMPT flag
for sense requests. This patch causes sense requests to be postponed while
a drive is suspended instead of being submitted to ide_queue_rq().

If it would ever be necessary to restore the IDE PREEMPT functionality,
that can be done by introducing a new flag in struct ide_request.

Link: https://lore.kernel.org/r/20201209052951.16136-4-bvanassche@acm.org
Cc: David S. Miller <davem@davemloft.net>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Can Guo <cang@codeaurora.org>
Cc: Stanley Chu <stanley.chu@mediatek.com>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-01-12 20:18:15 +01:00
arch s390: always clear kernel stack backchain before calling functions 2021-01-06 14:56:55 +01:00
block scsi: block: Introduce BLK_MQ_REQ_PM 2021-01-12 20:18:15 +01:00
certs .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
crypto crypto: ecdh - avoid unaligned accesses in ecdh_set_secret() 2020-12-30 11:54:10 +01:00
Documentation dt-bindings: rtc: add reset-source property 2021-01-09 13:46:22 +01:00
drivers scsi: ide: Do not set the RQF_PREEMPT flag for sense requests 2021-01-12 20:18:15 +01:00
fs exec: Transform exec_update_mutex into a rw_semaphore 2021-01-09 13:46:24 +01:00
include scsi: block: Introduce BLK_MQ_REQ_PM 2021-01-12 20:18:15 +01:00
init exec: Transform exec_update_mutex into a rw_semaphore 2021-01-09 13:46:24 +01:00
ipc ipc: adjust proc_ipc_sem_dointvec definition to match prototype 2020-09-05 12:14:29 -07:00
kernel workqueue: Kick a worker based on the actual activation of delayed works 2021-01-12 20:18:14 +01:00
lib zlib: move EXPORT_SYMBOL() and MODULE_LICENSE() out of dfltcc_syms.c 2021-01-06 14:56:51 +01:00
LICENSES LICENSES/deprecated: add Zlib license text 2020-09-16 14:33:49 +02:00
mm mm: memmap defer init doesn't work as expected 2021-01-06 14:56:50 +01:00
net erspan: fix version 1 check in gre_parse_header() 2021-01-12 20:18:12 +01:00
samples samples/bpf: Fix possible hang in xdpsock with multiple threads 2020-12-30 11:53:49 +01:00
scripts kconfig: fix return value of do_error_if() 2020-12-30 11:54:01 +01:00
security ima: Don't modify file descriptor mode on the fly 2020-12-30 11:54:17 +01:00
sound ALSA: hda/hdmi: Fix incorrect mutex unlock in silent_stream_disable() 2021-01-09 13:46:23 +01:00
tools selftests/vm: fix building protection keys test 2021-01-12 20:18:14 +01:00
usr Merge branch 'work.fdpic' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-08-07 13:29:39 -07:00
virt kvm: x86/mmu: Support dirty logging for the TDP MMU 2020-10-23 03:42:13 -04:00
.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 .gitignore: docs: ignore sphinx_*/ directories 2020-09-10 10:44:31 -06:00
.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 Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-12-10 15:30:13 -08:00
Makefile Linux 5.10.6 2021-01-09 13:46:25 +01:00
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.