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([14.38.141.199]) by cvnsmtp008.nm.naver.com with ESMTP id 3ptl+01VTsepfVkW+3ZiTQ for (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384); Tue, 27 Jan 2026 05:53:25 -0000 From: Minu Jin To: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, akpm@linux-foundation.org, david@kernel.org, kees@kernel.org Cc: dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Minu Jin Subject: [PATCH] fork: clarify copy_mm() comment for kernel thread Date: Tue, 27 Jan 2026 14:53:21 +0900 Message-ID: <20260127055321.2400480-1-s9430939@naver.com> X-Mailer: git-send-email 2.43.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: 1ytowfn6tn37x7mahczws7c56zef1tj4 X-Rspamd-Queue-Id: E403A1C0008 X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1769493210-420897 X-HE-Meta: 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 tLfgLcnR 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.344741, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: The existing comment is misleading: 1. "steal a active VM" suggests this code performs the active_mm borrowing, but the actual borrowing happens in context_switch() where 'next->active_mm = prev->active_mm' is assigned. This code simply returns 0 to skip mm copying for kernel threads. 2. "active VM" is outdated terminology, the kernel uses "active_mm". Update the comment to accurately describe what this code does. Signed-off-by: Minu Jin --- kernel/fork.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/fork.c b/kernel/fork.c index b1f3915d5f8e..4bfd606004db 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1566,9 +1566,10 @@ static int copy_mm(u64 clone_flags, struct task_struct *tsk) tsk->active_mm = NULL; /* - * Are we cloning a kernel thread? + * Kernel threads have no 'mm' of their own as they borrow the + * 'active_mm' from the previous process at context_switch(). * - * We need to steal a active VM for that.. + * Return 0 directly to skip the copy_mm process. */ oldmm = current->mm; if (!oldmm) -- 2.43.0