On Mon, Feb 10, 2025 at 12:05:05PM +0800, Qi Zheng wrote: > > > 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 <richard120310@xxxxxxxxx> > > --- > > 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); > > } Hi Qi, Thanks for your kindly review! > No. When start_pte is NULL, the ptl must also be NULL, so the ptl and > pml will not be equal. Since this is the case, we don't have to do any addtional check for "start_pte" and "ptl != pml", we can be sure that only the second check will be true so we can unlock "pml" without the redundant check, that's my understanding, what do you think? Best regards, I Hsin Cheng
