mainlining shenanigans
e4b9852a0f
Below two paths could overlap each other if we power off a drive quickly
after powering it on. There are multiple races in nvme_setup_io_queues()
because of shutdown_lock missing and improper use of NVMEQ_ENABLED bit.
nvme_reset_work() nvme_remove()
nvme_setup_io_queues() nvme_dev_disable()
... ...
A1 clear NVMEQ_ENABLED bit for admin queue lock
retry: B1 nvme_suspend_io_queues()
A2 pci_free_irq() admin queue B2 nvme_suspend_queue() admin queue
A3 pci_free_irq_vectors() nvme_pci_disable()
A4 nvme_setup_irqs(); B3 pci_free_irq_vectors()
... unlock
A5 queue_request_irq() for admin queue
set NVMEQ_ENABLED bit
...
nvme_create_io_queues()
A6 result = queue_request_irq();
set NVMEQ_ENABLED bit
...
fail to allocate enough IO queues:
A7 nvme_suspend_io_queues()
goto retry
If B3 runs in between A1 and A2, it will crash if irqaction haven't
been freed by A2. B2 is supposed to free admin queue IRQ but it simply
can't fulfill the job as A1 has cleared NVMEQ_ENABLED bit.
Fix: combine A1 A2 so IRQ get freed as soon as the NVMEQ_ENABLED bit
gets cleared.
After solved #1, A2 could race with B3 if A2 is freeing IRQ while B3
is checking irqaction. A3 also could race with B2 if B2 is freeing
IRQ while A3 is checking irqaction.
Fix: A2 and A3 take lock for mutual exclusion.
A3 could race with B3 since they could run free_msi_irqs() in parallel.
Fix: A3 takes lock for mutual exclusion.
A4 could fail to allocate all needed IRQ vectors if A3 and A4 are
interrupted by B3.
Fix: A4 takes lock for mutual exclusion.
If A5/A6 happened after B2/B1, B3 will crash since irqaction is not NULL.
They are just allocated by A5/A6.
Fix: Lock queue_request_irq() and setting of NVMEQ_ENABLED bit.
A7 could get chance to pci_free_irq() for certain IO queue while B3 is
checking irqaction.
Fix: A7 takes lock.
nvme_dev->online_queues need to be protected by shutdown_lock. Since it
is not atomic, both paths could modify it using its own copy.
Co-developed-by: Yuanyuan Zhong <yzhong@purestorage.com>
Signed-off-by: Casey Chen <cachen@purestorage.com>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
|
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| 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.