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Wed, 21 Feb 2024 22:21:14 +0900 (JST) (envelope-from penguin-kernel@I-love.SAKURA.ne.jp) Message-ID: Date: Wed, 21 Feb 2024 22:21:04 +0900 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 31/35] lib: add memory allocations report in show_mem() To: Vlastimil Babka , Suren Baghdasaryan , Kent Overstreet Cc: Steven Rostedt , Michal Hocko , akpm@linux-foundation.org, hannes@cmpxchg.org, roman.gushchin@linux.dev, mgorman@suse.de, dave@stgolabs.net, willy@infradead.org, liam.howlett@oracle.com, corbet@lwn.net, void@manifault.com, peterz@infradead.org, juri.lelli@redhat.com, catalin.marinas@arm.com, will@kernel.org, arnd@arndb.de, tglx@linutronix.de, mingo@redhat.com, dave.hansen@linux.intel.com, x86@kernel.org, peterx@redhat.com, david@redhat.com, axboe@kernel.dk, mcgrof@kernel.org, masahiroy@kernel.org, nathan@kernel.org, dennis@kernel.org, tj@kernel.org, muchun.song@linux.dev, rppt@kernel.org, paulmck@kernel.org, pasha.tatashin@soleen.com, yosryahmed@google.com, yuzhao@google.com, dhowells@redhat.com, hughd@google.com, andreyknvl@gmail.com, keescook@chromium.org, ndesaulniers@google.com, vvvvvv@google.com, gregkh@linuxfoundation.org, ebiggers@google.com, ytcoode@gmail.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, bsegall@google.com, bristot@redhat.com, vschneid@redhat.com, cl@linux.com, penberg@kernel.org, iamjoonsoo.kim@lge.com, 42.hyeyoo@gmail.com, glider@google.com, elver@google.com, dvyukov@google.com, shakeelb@google.com, songmuchun@bytedance.com, jbaron@akamai.com, rientjes@google.com, minchan@google.com, kaleshsingh@google.com, kernel-team@android.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, iommu@lists.linux.dev, linux-arch@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-modules@vger.kernel.org, kasan-dev@googlegroups.com, cgroups@vger.kernel.org References: <320cd134-b767-4f29-869b-d219793ba8a1@suse.cz> <20240215180742.34470209@gandalf.local.home> <20240215181648.67170ed5@gandalf.local.home> <20240215182729.659f3f1c@gandalf.local.home> Content-Language: en-US From: Tetsuo Handa In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: C62631C000A X-Stat-Signature: x939qy641hhop3r8w7d64dq3hcb4wiqr X-HE-Tag: 1708521784-326372 X-HE-Meta: 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 LSVOAWuR 3l8O0wqrOK5OQr1byQ+xrKKkcNQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2024/02/21 3:27, Vlastimil Babka wrote: > I'm sure more such scenarios exist, Cc: Tetsuo who I recall was an expert on > this topic. "[PATCH v3 10/35] lib: code tagging framework" says that codetag_lock_module_list() calls down_read() (i.e. sleeping operation), and "[PATCH v3 31/35] lib: add memory allocations report in show_mem()" says that __show_mem() calls alloc_tags_show_mem_report() after kmalloc(GFP_ATOMIC) (i.e. non-sleeping operation) but alloc_tags_show_mem_report() calls down_read() via codetag_lock_module_list() !? If __show_mem() might be called from atomic context (e.g. kmalloc(GFP_ATOMIC)), this will be a sleep in atomic bug. If __show_mem() might be called while semaphore is held for write, this will be a read-lock after write-lock deadlock bug. Not the matter of whether to allocate buffer statically or dynamically. Please don't hold a lock when trying to report memory usage.