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5d808c78d9
We met a SCHED_WARN in set_next_buddy():
__warn_printk
set_next_buddy
yield_to_task_fair
yield_to
kvm_vcpu_yield_to [kvm]
...
After a short dig, we found the rq_lock held by yield_to() may not
be exactly the rq that the target task belongs to. There is a race
window against try_to_wake_up().
CPU0 target_task
blocking on CPU1
lock rq0 & rq1
double check task_rq == p_rq, ok
woken to CPU2 (lock task_pi & rq2)
task_rq = rq2
yield_to_task_fair (w/o lock rq2)
In this race window, yield_to() is operating the task w/o the correct
lock. Fix this by taking task pi_lock first.
Fixes: d95f412200 ("sched: Add yield_to(task, preempt) functionality")
Signed-off-by: Tianchen Ding <dtcccc@linux.alibaba.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20241231055020.6521-1-dtcccc@linux.alibaba.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 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.