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Sun, 09 Feb 2025 20:05:09 -0800 (PST) Message-ID: Date: Mon, 10 Feb 2025 12:05:05 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: pgtable: Ensure pml spinlock gets unlock Content-Language: en-US To: I Hsin Cheng Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20250208184928.219960-1-richard120310@gmail.com> From: Qi Zheng In-Reply-To: <20250208184928.219960-1-richard120310@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2025/2/9 02:49, I Hsin Cheng wrote: > When !start_pte is true, the "pml" spinlock is still being holded and > the branch "out_pte" is taken. If "ptl" is equal to "pml", the lock > "pml" will still be locked when the function returns. No. When start_pte is NULL, the ptl must also be NULL, so the ptl and pml will not be equal. > > It'll be better to set a new branch "out_pte" and jump to it when > !start_pte is true at the first place, therefore no additional check for > "start_pte" or "ptl != pml" is needed, simply unlock "pml" and return. > > Signed-off-by: I Hsin Cheng > --- > mm/pt_reclaim.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/mm/pt_reclaim.c b/mm/pt_reclaim.c > index 7e9455a18aae..163e38f1728d 100644 > --- a/mm/pt_reclaim.c > +++ b/mm/pt_reclaim.c > @@ -43,7 +43,7 @@ void try_to_free_pte(struct mm_struct *mm, pmd_t *pmd, unsigned long addr, > pml = pmd_lock(mm, pmd); > start_pte = pte_offset_map_rw_nolock(mm, pmd, addr, &pmdval, &ptl); > if (!start_pte) > - goto out_ptl; > + goto out_pte; > if (ptl != pml) > spin_lock_nested(ptl, SINGLE_DEPTH_NESTING); > > @@ -68,4 +68,8 @@ void try_to_free_pte(struct mm_struct *mm, pmd_t *pmd, unsigned long addr, > pte_unmap_unlock(start_pte, ptl); > if (ptl != pml) > spin_unlock(pml); > + return; > + > +out_pte: > + spin_unlock(pml); > }