2c06479884
ioc_qos_write() and ioc_cost_model_write() are the same: 1) hold lock to read 'ioc->params' to local variable; 2) update params to local variable without lock; 3) hold lock to write local variable to 'ioc->params'; In theroy, if user updates params concurrenty, the params might be lost: t1: update params a t2: update params b spin_lock_irq(&ioc->lock); memcpy(qos, ioc->params.qos, sizeof(qos)) spin_unlock_irq(&ioc->lock); qos[a] = xxx; spin_lock_irq(&ioc->lock); memcpy(qos, ioc->params.qos, sizeof(qos)) spin_unlock_irq(&ioc->lock); qos[b] = xxx; spin_lock_irq(&ioc->lock); memcpy(ioc->params.qos, qos, sizeof(qos)); ioc_refresh_params(ioc, true); spin_unlock_irq(&ioc->lock); spin_lock_irq(&ioc->lock); // updates of a will be lost memcpy(ioc->params.qos, qos, sizeof(qos)); ioc_refresh_params(ioc, true); spin_unlock_irq(&ioc->lock); Althrough this is not common case, the problem can by fixed easily by holding the lock through the read, update, write process. Signed-off-by: Yu Kuai <yukuai3@huawei.com> Acked-by: Tejun Heo <tj@kernel.org> Link: https://lore.kernel.org/r/20221012094035.390056-3-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
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.