Message ID | 20230619090336.145738-1-mmpgouride@gmail.com |
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State | New |
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Series |
list: Remove unnecessary WRITE_ONCE()
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Commit Message
Alan Huang
June 19, 2023, 9:03 a.m. UTC
Commit c54a2744497d("list: Add hlist_unhashed_lockless()") added
various WRITE_ONCE() to pair with the READ_ONCE() in
hlist_unhashed_lockless(), but there is no need to protect
->next with WRITE_ONCE(). Therefore, this commit removes those
unnecessary WRITE_ONCE().
Signed-off-by: Alan Huang <mmpgouride@gmail.com>
---
include/linux/list.h | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
Comments
On Mon, Jun 19, 2023 at 11:03 AM Alan Huang <mmpgouride@gmail.com> wrote: > > Commit c54a2744497d("list: Add hlist_unhashed_lockless()") added > various WRITE_ONCE() to pair with the READ_ONCE() in > hlist_unhashed_lockless(), but there is no need to protect > ->next with WRITE_ONCE(). Therefore, this commit removes those > unnecessary WRITE_ONCE(). Why are they unnecessary ? They seem just fine to me. Please elaborate.
> 2023年6月19日 19:02,Eric Dumazet <edumazet@google.com> 写道: > > On Mon, Jun 19, 2023 at 11:03 AM Alan Huang <mmpgouride@gmail.com> wrote: >> >> Commit c54a2744497d("list: Add hlist_unhashed_lockless()") added >> various WRITE_ONCE() to pair with the READ_ONCE() in >> hlist_unhashed_lockless(), but there is no need to protect >> ->next with WRITE_ONCE(). Therefore, this commit removes those >> unnecessary WRITE_ONCE(). > > Why are they unnecessary ? There is no reader locklessly read ->next. These functions are protected by something like spin_lock, only the thread running the function can access ->next. > They seem just fine to me. > Please elaborate.
Hi Paul, Looks like you missed this one? Thanks, Alan > 2023年6月19日 17:03,Alan Huang <mmpgouride@gmail.com> 写道: > > Commit c54a2744497d("list: Add hlist_unhashed_lockless()") added > various WRITE_ONCE() to pair with the READ_ONCE() in > hlist_unhashed_lockless(), but there is no need to protect > ->next with WRITE_ONCE(). Therefore, this commit removes those > unnecessary WRITE_ONCE(). > > Signed-off-by: Alan Huang <mmpgouride@gmail.com> > --- > include/linux/list.h | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/include/linux/list.h b/include/linux/list.h > index f10344dbad..ac366958ea 100644 > --- a/include/linux/list.h > +++ b/include/linux/list.h > @@ -940,7 +940,7 @@ static inline void hlist_del_init(struct hlist_node *n) > static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h) > { > struct hlist_node *first = h->first; > - WRITE_ONCE(n->next, first); > + n->next = first; > if (first) > WRITE_ONCE(first->pprev, &n->next); > WRITE_ONCE(h->first, n); > @@ -956,7 +956,7 @@ static inline void hlist_add_before(struct hlist_node *n, > struct hlist_node *next) > { > WRITE_ONCE(n->pprev, next->pprev); > - WRITE_ONCE(n->next, next); > + n->next = next; > WRITE_ONCE(next->pprev, &n->next); > WRITE_ONCE(*(n->pprev), n); > } > @@ -969,8 +969,8 @@ static inline void hlist_add_before(struct hlist_node *n, > static inline void hlist_add_behind(struct hlist_node *n, > struct hlist_node *prev) > { > - WRITE_ONCE(n->next, prev->next); > - WRITE_ONCE(prev->next, n); > + n->next = prev->next; > + prev->next = n; > WRITE_ONCE(n->pprev, &prev->next); > > if (n->next) > -- > 2.34.1 >
diff --git a/include/linux/list.h b/include/linux/list.h index f10344dbad..ac366958ea 100644 --- a/include/linux/list.h +++ b/include/linux/list.h @@ -940,7 +940,7 @@ static inline void hlist_del_init(struct hlist_node *n) static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h) { struct hlist_node *first = h->first; - WRITE_ONCE(n->next, first); + n->next = first; if (first) WRITE_ONCE(first->pprev, &n->next); WRITE_ONCE(h->first, n); @@ -956,7 +956,7 @@ static inline void hlist_add_before(struct hlist_node *n, struct hlist_node *next) { WRITE_ONCE(n->pprev, next->pprev); - WRITE_ONCE(n->next, next); + n->next = next; WRITE_ONCE(next->pprev, &n->next); WRITE_ONCE(*(n->pprev), n); } @@ -969,8 +969,8 @@ static inline void hlist_add_before(struct hlist_node *n, static inline void hlist_add_behind(struct hlist_node *n, struct hlist_node *prev) { - WRITE_ONCE(n->next, prev->next); - WRITE_ONCE(prev->next, n); + n->next = prev->next; + prev->next = n; WRITE_ONCE(n->pprev, &prev->next); if (n->next)