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Patch series "mm/kmemleak: Avoid soft lockup in kmemleak_scan()", v2. There are 3 RCU-based object iteration loops in kmemleak_scan(). Because of the need to take RCU read lock, we can't insert cond_resched() into the loop like other parts of the function. As there can be millions of objects to be scanned, it takes a while to iterate all of them. The kmemleak functionality is usually enabled in a debug kernel which is much slower than a non-debug kernel. With sufficient number of kmemleak objects, the time to iterate them all may exceed 22s causing soft lockup. watchdog: BUG: soft lockup - CPU#3 stuck for 22s! [kmemleak:625] This patch series make changes to the 3 object iteration loops in kmemleak_scan() to prevent them from causing soft lockup. This patch (of 3): kmemleak_scan() is called only from the kmemleak scan thread or from write to the kmemleak debugfs file. Both are in task context and so we can directly use the simpler _irq() lock/unlock calls instead of the more complex _irqsave/_irqrestore variants. Similarly, kmemleak_clear() is called only from write to the kmemleak debugfs file. The same change can be applied. Link: https://lkml.kernel.org/r/20220614220359.59282-1-longman@redhat.com Link: https://lkml.kernel.org/r/20220614220359.59282-2-longman@redhat.com Signed-off-by: Waiman Long <longman@redhat.com> Reviewed-by: Muchun Song <songmuchun@bytedance.com> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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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.