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Bart Van Assche eb3e975ac2 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 20:16:09 +01:00
Documentation x86/CPU/AMD: Save AMD NodeId as cpu_die_id 2020-12-30 11:51:47 +01:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
arch um: ubd: Submit all data segments atomically 2021-01-06 14:48:40 +01:00
block scsi: block: Fix a race in the runtime power management code 2021-01-06 14:48:37 +01:00
certs PKCS#7: Refactor verify_pkcs7_signature() 2019-08-05 18:40:18 -04:00
crypto crypto: ecdh - avoid unaligned accesses in ecdh_set_secret() 2020-12-30 11:51:35 +01:00
drivers scsi: ide: Do not set the RQF_PREEMPT flag for sense requests 2021-01-12 20:16:09 +01:00
fs exec: Transform exec_update_mutex into a rw_semaphore 2021-01-09 13:44:55 +01:00
include exec: Transform exec_update_mutex into a rw_semaphore 2021-01-09 13:44:55 +01:00
init exec: Transform exec_update_mutex into a rw_semaphore 2021-01-09 13:44:55 +01:00
ipc ipc/util.c: sysvipc_find_ipc() incorrectly updates position index 2020-05-20 08:20:16 +02:00
kernel workqueue: Kick a worker based on the actual activation of delayed works 2021-01-12 20:16:09 +01:00
lib lib/syscall: fix syscall registers retrieval on 32-bit platforms 2020-12-11 13:23:32 +01:00
mm mm: don't wake kswapd prematurely when watermark boosting is disabled 2020-12-30 11:51:27 +01:00
net net/sched: sch_taprio: reset child qdiscs before freeing them 2021-01-06 14:48:35 +01:00
samples samples: bpf: Fix lwt_len_hist reusing previous BPF map 2020-12-30 11:51:12 +01:00
scripts kconfig: fix return value of do_error_if() 2020-12-30 11:51:29 +01:00
security ima: Don't modify file descriptor mode on the fly 2020-12-30 11:51:39 +01:00
sound ALSA: pcm: Clear the full allocated memory at hw_params 2021-01-06 14:48:40 +01:00
tools tools headers UAPI: Sync linux/const.h with the kernel headers 2021-01-06 14:48:37 +01:00
usr initramfs: restore default compression behavior 2020-04-08 09:08:38 +02:00
virt KVM: arm64: vgic-v3: Drop the reporting of GICR_TYPER.Last for userspace 2020-12-02 08:49:46 +01:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Modules updates for v5.4 2019-09-22 10:34:46 -07:00
.mailmap ARM: SoC fixes 2019-11-10 13:41:59 -08:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS: Remove Simon as Renesas SoC Co-Maintainer 2019-10-10 08:12:51 -07:00
Kbuild kbuild: do not descend to ./Kbuild when cleaning 2019-08-21 21:03:58 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS Documentation/llvm: add documentation on building w/ Clang/LLVM 2020-08-26 10:40:46 +02:00
Makefile Linux 5.4.88 2021-01-09 13:44:55 +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.