From: Wei Yang <richard.weiyang@xxxxxxxxxxxxxxxxx> Subject: mm/mempolicy: remove or narrow the lock on current It is not necessary to hold the lock of current when setting nodemask of a new policy. Link: https://lkml.kernel.org/r/20200921040416.86185-1-richard.weiyang@xxxxxxxxxxxxxxxxx Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxxxxxxxxxx> Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/mempolicy.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) --- a/mm/mempolicy.c~mm-mempolicy-remove-or-narrow-the-lock-on-current +++ a/mm/mempolicy.c @@ -875,13 +875,12 @@ static long do_set_mempolicy(unsigned sh goto out; } - task_lock(current); ret = mpol_set_nodemask(new, nodes, scratch); if (ret) { - task_unlock(current); mpol_put(new); goto out; } + task_lock(current); old = current->mempolicy; current->mempolicy = new; if (new && new->mode == MPOL_INTERLEAVE) @@ -1324,9 +1323,7 @@ static long do_mbind(unsigned long start NODEMASK_SCRATCH(scratch); if (scratch) { mmap_write_lock(mm); - task_lock(current); err = mpol_set_nodemask(new, nmask, scratch); - task_unlock(current); if (err) mmap_write_unlock(mm); } else _
