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ca6263a0c9
With some spi devices, the heavy cpu usage due to polling the spi registers may lead to netdev timeouts, RCU complaints, etc. This can be acute in the absence of CONFIG_PREEMPT. This patch allows to give enough breathing room to avoid those incorrectly detected netdev timeouts for example. Example splat on 5.10.92: [ 828.399306] rcu: INFO: rcu_sched self-detected stall on CPU ... [ 828.419245] Task dump for CPU 1: [ 828.422465] task:kworker/1:1H state:R running task on cpu 1 stack: 0 pid: 76 ppid: 2 flags:0x0000002a [ 828.433132] Workqueue: kblockd blk_mq_run_work_fn [ 828.437820] Call trace: ... [ 828.512267] spi_mem_exec_op+0x4d0/0xde0 [ 828.516184] spi_mem_dirmap_read+0x180/0x39c [ 828.520443] spi_nor_read_data+0x428/0x7e8 [ 828.524523] spi_nor_read+0x154/0x214 [ 828.528172] mtd_read_oob+0x440/0x714 [ 828.531815] mtd_read+0xac/0x120 [ 828.535030] mtdblock_readsect+0x178/0x230 [ 828.539102] mtd_blktrans_work+0x9fc/0xf28 [ 828.543177] mtd_queue_rq+0x1ac/0x2e4 [ 828.546827] blk_mq_dispatch_rq_list+0x2cc/0xa44 [ 828.551419] blk_mq_do_dispatch_sched+0xb0/0x7cc [ 828.556010] __blk_mq_sched_dispatch_requests+0x350/0x494 [ 828.561372] blk_mq_sched_dispatch_requests+0xac/0xe4 [ 828.566387] __blk_mq_run_hw_queue+0x130/0x254 [ 828.570806] blk_mq_run_work_fn+0x50/0x60 [ 828.574814] process_one_work+0x578/0xf1c [ 828.578814] worker_thread+0x5dc/0xea0 [ 828.582547] kthread+0x270/0x2d4 [ 828.585765] ret_from_fork+0x10/0x30 Signed-off-by: David Decotigny <ddecotig@google.com> Reviewed-by: Richard Weinberger <richard@nod.at> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com> Link: https://lore.kernel.org/linux-mtd/20220126101120.676021-1-decot+git@google.com
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.