Re: pserialize-safe queue(3) alternative

[Kengo NAKAHARA <k-nakahara%iij.ad.jp@localhost>]

Hi,

Thank you for quick update!

On 2016/04/08 1:09, Taylor R Campbell wrote:
>    Date: Thu, 7 Apr 2016 18:22:08 +0900
>    From: Kengo NAKAHARA <k-nakahara%iij.ad.jp@localhost>
> 
>    Sorry, I found one more question. _pslist_writer_next_container() does
>    not use "next" variable. I think the following patch is required.
> 
> Thanks!  Here's a new draft with this fix, the insert_after fix, and a
> note on write ordering to justify the placement of membar_producer.

I apply pslist to my gif(4) implementation. Furthermore, ozaki-r@n.o
apply pslist to bridge(4) and check by ATF. In consequence, we think
the following patch might be required. Is the patch appropriate?

====================
diff --git a/sys/sys/pslist.h b/sys/sys/pslist.h
index 2aef4b3..a59713e 100644
--- a/sys/sys/pslist.h
+++ b/sys/sys/pslist.h
@@ -73,6 +73,8 @@ static inline void
 pslist_writer_insert_head(struct pslist_head *head, struct pslist_entry *new)
 {
 
+       if (head->plh_first != NULL)
+               head->plh_first->ple_prevp = &new->ple_next;
        new->ple_prevp = &head->plh_first;
        new->ple_next = head->plh_first;
        membar_producer();
@@ -107,6 +109,8 @@ static inline void
 pslist_writer_remove(struct pslist_entry *entry)
 {
 
+       if (entry->ple_next != NULL)
+               entry->ple_next->ple_prevp = entry->ple_prevp;
        *entry->ple_prevp = entry->ple_next;
        entry->ple_prevp = NULL; /* poison */
 }
@@ -187,7 +191,7 @@ _pslist_reader_next_container(struct pslist_entry *entry, ptrdiff_t offset)
 {
        struct pslist_entry *next = entry->ple_next;
 
-       if (entry == NULL)
+       if (next == NULL)
                return NULL;
        membar_datadep_consumer();
 
@@ -224,10 +228,10 @@ _pslist_reader_next_container(struct pslist_entry *entry, ptrdiff_t offset)
        pslist_writer_remove(&(E)->F)
 #define        PSLIST_WRITER_FIRST(H, T, F)                                          \
        ((T *)(_pslist_writer_first_container((H), offsetof(T, F))) +         \
-           _PSLIST_VALIDATE_CONTAINER(pslist_first(H), T, F))
+           _PSLIST_VALIDATE_CONTAINER(pslist_writer_first(H), T, F))
 #define        PSLIST_WRITER_NEXT(V, T, F)                                           \
        ((T *)(_pslist_writer_next_container(&(V)->F, offsetof(T, F))) +      \
-           _PSLIST_VALIDATE_CONTAINER(pslist_next(&(V)->F), T, F))
+           _PSLIST_VALIDATE_CONTAINER(pslist_writer_next(&(V)->F), T, F))
 #define        PSLIST_WRITER_FOREACH(V, H, T, F)                                     \
        for ((V) = PSLIST_WRITER_FIRST((H), T, F);                            \
                (V) != NULL;                                                  \
@@ -235,10 +239,10 @@ _pslist_reader_next_container(struct pslist_entry *entry, ptrdiff_t offset)
 
 #define        PSLIST_READER_FIRST(H, T, F)                                          \
        ((T *)(_pslist_reader_first_container((H), offsetof(T, F))) +         \
-           _PSLIST_VALIDATE_CONTAINER(pslist_first(H), T, F))
+           _PSLIST_VALIDATE_CONTAINER(pslist_reader_first(H), T, F))
 #define        PSLIST_READER_NEXT(V, T, F)                                           \
        ((T *)(_pslist_reader_next_container(&(V)->F, offsetof(T, F))) +      \
-           _PSLIST_VALIDATE_CONTAINER(pslist_next(&(V)->F), T, F))
+           _PSLIST_VALIDATE_CONTAINER(pslist_reader_next(&(V)->F), T, F))
 #define        PSLIST_READER_FOREACH(V, H, T, F)                                     \
        for ((V) = PSLIST_READER_FIRST((H), T, F);                            \
                (V) != NULL;                                                  \
====================


Thanks,

-- 
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Internet Initiative Japan Inc.

Device Engineering Section,
IoT Platform Development Department,
Network Division,
Technology Unit

Kengo NAKAHARA <k-nakahara%iij.ad.jp@localhost>