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Be conservative about alignment requirements of struct epoll_event.

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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().

Found by myself while testing on an Sun Ultra 5 (Sparc IIi) with some
editorializing by Andres Freund.

In passing fix a couple typos in the area
This commit is contained in:
Greg Stark 2016-06-02 19:23:25 +01:00
parent 4edb7bd2fd
commit a3b30763cc
1 changed files with 18 additions and 12 deletions
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30
src/backend/storage/ipc/latch.c
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@ -475,7 +475,7 @@ ResetLatch(volatile Latch *latch)
/*
* Create a WaitEventSet with space for nevents different events to wait for.
*
* These events can then efficiently waited upon together, using
* These events can then be efficiently waited upon together, using
* WaitEventSetWait().
*/
WaitEventSet *
@ -485,35 +485,41 @@ CreateWaitEventSet(MemoryContext context, int nevents)
char *data;
Size sz = 0;
sz += sizeof(WaitEventSet);
sz += sizeof(WaitEvent) * nevents;
/*
* 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
set->latch = NULL;
@ -616,7 +622,7 @@ AddWaitEventToSet(WaitEventSet *set, uint32 events, pgsocket fd, Latch *latch,
if (set->latch)
elog(ERROR, "cannot wait on more than one latch");
if ((events & WL_LATCH_SET) != WL_LATCH_SET)
elog(ERROR, "latch events only spuport being set");
elog(ERROR, "latch events only support being set");
}
else
{