mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2026-09-22 09:34:56 +02:00
Ming Lei
15dba511d5
[ Upstream commit87d0740b7c] dev->nthreads is derived from the user-requested queue count before the ADD command, but the kernel may reduce nr_hw_queues (capped to nr_cpu_ids). When the VM has fewer CPUs than requested queues, the daemon creates more handler threads than there are kernel queues. In non-batch mode, the extra threads access uninitialized queues (q_depth=0), submit zero io_uring SQEs, and block forever in io_cqring_wait. In batch mode, the extra threads cause similar hangs during device removal. In both cases, the stuck threads prevent the daemon from closing the char device, holding the last ublk_device reference and causing ublk_ctrl_del_dev() to hang in wait_event_interruptible(). Fix by capping dev->nthreads to the kernel-returned nr_hw_queues after the ADD command completes. per_io_tasks mode is excluded because threads interleave across all queues, so nthreads > nr_hw_queues is valid. Fixes:abe54c1603("selftests: ublk: kublk: decouple ublk_queues from ublk server threads") Signed-off-by: Ming Lei <tom.leiming@gmail.com> Link: https://patch.msgid.link/20260513101941.1373998-1-tom.leiming@gmail.com Signed-off-by: Jens Axboe <axboe@kernel.dk> 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 reStructuredText 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.