Hi, On 2016-06-02 19:15:07 +0100, Greg Stark wrote: > Ok. I added a comment and also fixed a small typo.
> diff --git a/src/backend/storage/ipc/latch.c b/src/backend/storage/ipc/latch.c > index 3fbe0e5..a96fb7b 100644 > --- a/src/backend/storage/ipc/latch.c > +++ b/src/backend/storage/ipc/latch.c > @@ -485,35 +485,40 @@ CreateWaitEventSet(MemoryContext context, int nevents) > char *data; > Size sz = 0; > > - sz += sizeof(WaitEventSet); > - sz += sizeof(WaitEvent) * nevents; > + /* > + * struct epoll_event contains a uint64_t which on some architectures > + * requires 8-byte alignment and just to be safe be prepared for future > + * additions of other such elements later in the WaitEventSet structure > + */ I'd rather phrase this roughly like: Use MAXALIGN size/alignment to guarantee that later uses of memory are aligned correctly. E.g. epoll_event might need 8 byte alignment on some platforms, but earlier allocations like WaitEventSet and WaitEvent might not sized to guarantee that when purely using sizeof(). > + sz += MAXALIGN(sizeof(WaitEventSet)); > + sz += MAXALIGN(sizeof(WaitEvent) * nevents); > > #if defined(WAIT_USE_EPOLL) > - sz += sizeof(struct epoll_event) * nevents; > + sz += MAXALIGN(sizeof(struct epoll_event) * nevents); > #elif defined(WAIT_USE_POLL) > - sz += sizeof(struct pollfd) * nevents; > + sz += MAXALIGN(sizeof(struct pollfd) * nevents); > #elif defined(WAIT_USE_WIN32) > /* need space for the pgwin32_signal_event */ > - sz += sizeof(HANDLE) * (nevents + 1); > + sz += MAXALIGN(sizeof(HANDLE) * (nevents + 1)); > #endif > > data = (char *) MemoryContextAllocZero(context, sz); > > set = (WaitEventSet *) data; > - data += sizeof(WaitEventSet); > + data += MAXALIGN(sizeof(WaitEventSet)); > > set->events = (WaitEvent *) data; > - data += sizeof(WaitEvent) * nevents; > + data += MAXALIGN(sizeof(WaitEvent) * nevents); > > #if defined(WAIT_USE_EPOLL) > set->epoll_ret_events = (struct epoll_event *) data; > - data += sizeof(struct epoll_event) * nevents; > + data += MAXALIGN(sizeof(struct epoll_event) * nevents); > #elif defined(WAIT_USE_POLL) > set->pollfds = (struct pollfd *) data; > - data += sizeof(struct pollfd) * nevents; > + data += MAXALIGN(sizeof(struct pollfd) * nevents); > #elif defined(WAIT_USE_WIN32) > set->handles = (HANDLE) data; > - data += sizeof(HANDLE) * nevents; > + data += MAXALIGN(sizeof(HANDLE) * nevents); > #endif You can't easily test WIN32, but I'd suggest running make check with WAIT_USE_POLL and WAIT_USE_SELECT at the top. Looks sane otherwise. Greetings, Andres Freund -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
