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[ Upstream commit745e10146c] "cat /proc/slab_allocators" could hang forever on SMP machines with kmemleak or object debugging enabled due to other CPUs running do_drain() will keep making kmemleak_object or debug_objects_cache dirty and unable to escape the first loop in leaks_show(), do { set_store_user_clean(cachep); drain_cpu_caches(cachep); ... } while (!is_store_user_clean(cachep)); For example, do_drain slabs_destroy slab_destroy kmem_cache_free __cache_free ___cache_free kmemleak_free_recursive delete_object_full __delete_object put_object free_object_rcu kmem_cache_free cache_free_debugcheck --> dirty kmemleak_object One approach is to check cachep->name and skip both kmemleak_object and debug_objects_cache in leaks_show(). The other is to set store_user_clean after drain_cpu_caches() which leaves a small window between drain_cpu_caches() and set_store_user_clean() where per-CPU caches could be dirty again lead to slightly wrong information has been stored but could also speed up things significantly which sounds like a good compromise. For example, # cat /proc/slab_allocators 0m42.778s # 1st approach 0m0.737s # 2nd approach [akpm@linux-foundation.org: tweak comment] Link: http://lkml.kernel.org/r/20190411032635.10325-1-cai@lca.pw Fixes:d31676dfde("mm/slab: alternative implementation for DEBUG_SLAB_LEAK") Signed-off-by: Qian Cai <cai@lca.pw> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Christoph Lameter <cl@linux.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: David Rientjes <rientjes@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.