8e781506a7
[ Upstream commit e7dcc514a49e74051b869697d5ab0370f6301d57 ] IRQ polling thread calls ISR after enable_irq() to handle any missed I/O completion. The atomic flag "in_used" was added to have the synchronization between the IRQ polling thread and the interrupt context. There is a bug around it leading to a race condition. Below is the sequence: - IRQ polling thread accesses ISR, fetches the reply descriptor. - Real interrupt arrives and pre-empts polling thread (enable_irq() is already called). - Interrupt context picks the same reply descriptor as fetched by polling thread, processes it, and exits. - Polling thread resumes and processes the descriptor which is already processed by interrupt thread leads to kernel crash. Setting the "in_used" flag before fetching the reply descriptor ensures synchronized access to ISR. Link: https://www.spinics.net/lists/linux-scsi/msg159440.html Link: https://lore.kernel.org/r/20210929124022.24605-2-sumit.saxena@broadcom.com Fixes: 9bedd36e9146 ("scsi: megaraid_sas: Handle missing interrupts while re-enabling IRQs") Signed-off-by: Sumit Saxena <sumit.saxena@broadcom.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
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.