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Shutemov" Cc: akpm@linux-foundation.org, vbabka@suse.cz, surenb@google.com, mhocko@suse.com, jackmanb@google.com, hannes@cmpxchg.org, tglx@linutronix.de, david@redhat.com, ast@kernel.org, linux-mm@kvack.org, linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH 2/2] mm/page_alloc: Fix race condition in unaccepted memory handling Message-ID: <20250506124341.GDaBoD_cYkXsnTmRdj@fat_crate.local> References: <20250506112509.905147-1-kirill.shutemov@linux.intel.com> <20250506112509.905147-3-kirill.shutemov@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20250506112509.905147-3-kirill.shutemov@linux.intel.com> X-Stat-Signature: fbheh7egfj3ifhnrg6hus9obfcxz4t6f X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 170CA40011 X-Rspam-User: X-HE-Tag: 1746535448-324373 X-HE-Meta: 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 zl6S0P2V TmmT/b2Jwp7dyj/+Top2FOyCNejnBcBtNRl4FgnDPIt6LTA4FQUDdxcv6ZaUBRC667t8/5Ofc31X7QF0VfWiSdwp0bVpvS3PlfNnmwAYWx6IlWhNvAF/NseXvjTWMuAufq8nYb4BVAIJ81oVZq4tb/jbTMkyXP7J52GL8cjyd3uIOCPTIueZXZf4fp8r/prriRoHEEJ1bg+ZnuUyt328S3Sc+b78M9exGVfYtZPJ3DnQxSHgNI0swAcc0BDVko8YhkxqJJOUQSkQ+3EW8YFPn2IcpZKbAwEQt2oYemyDAnft0hOJBIQnbiiFy+NHbZyXaKzfUDCOzVgVfDFKhf2OfqDmplA== 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 Tue, May 06, 2025 at 02:25:09PM +0300, Kirill A. Shutemov wrote: > The page allocator tracks the number of zones that have unaccepted > memory using static_branch_enc/dec() and uses that static branch in hot > paths to determine if it needs to deal with unaccepted memory. > > Borisal and Thomas pointed out that the tracking is racy operations on Boris or Borislav would be nice. > static_branch are not serialized against adding/removing unaccepted pages > to/from the zone. Also, that sentence needs massaging. > The effect of this static_branch optimization is only visible on > microbenchmark. > > Instead of adding more complexity around it, remove it altogether. Yah, good idea. > Signed-off-by: Kirill A. Shutemov > Fixes: dcdfdd40fa82 ("mm: Add support for unaccepted memory") > Link: https://lore.kernel.org/all/20250506092445.GBaBnVXXyvnazly6iF@fat_crate.local > Reported-by: Borislav Petkov Tested-by: Borislav Petkov (AMD) Thx for the quick fix. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette