We've long had reports of intermittent "could not reattach to shared
memory" errors on Windows. Buildfarm member dory fails that way when
PGSharedMemoryReAttach() execution overlaps with creation of a thread
for the process's "default thread pool". Fix that by providing a second
region to receive asynchronous allocations that would otherwise intrude
into UsedShmemSegAddr. In pgwin32_ReserveSharedMemoryRegion(), stop
trying to free reservations landing at incorrect addresses; the caller's
next step has been to terminate the affected process. Back-patch to 9.4
(all supported versions).
Reviewed by Tom Lane. He also did much of the prerequisite research;
see commit bcbf2346d6.
Discussion: https://postgr.es/m/20190402135442.GA1173872@rfd.leadboat.com
postmaster startup scrutinizes any shared memory segment recorded in
postmaster.pid, exiting if that segment matches the current data
directory and has an attached process. When the postmaster.pid file was
missing, a starting postmaster used weaker checks. Change to use the
same checks in both scenarios. This increases the chance of a startup
failure, in lieu of data corruption, if the DBA does "kill -9 `head -n1
postmaster.pid` && rm postmaster.pid && pg_ctl -w start". A postmaster
will no longer recycle segments pertaining to other data directories.
That's good for production, but it's bad for integration tests that
crash a postmaster and immediately delete its data directory. Such a
test now leaks a segment indefinitely. No "make check-world" test does
that. win32_shmem.c already avoided all these problems. In 9.6 and
later, enhance PostgresNode to facilitate testing. Back-patch to 9.4
(all supported versions).
Reviewed by Daniel Gustafsson and Kyotaro HORIGUCHI.
Discussion: https://postgr.es/m/20130911033341.GD225735@tornado.leadboat.com
Revert the map/unmap dance I tried in commit 73042b8d1; that helps
not at all.
Instead, speculate that the unwanted allocation is being done on
another thread, and thus timing variations explain the apparent
unpredictability. Temporarily add a 1-second sleep before the
VirtualFree call, in hopes that any such other threads will
quiesce and not jog our elbow.
This is obviously not a desirable long-term fix, but as a means of
investigation it seems useful.
Discussion: https://postgr.es/m/25495.1524517820@sss.pgh.pa.us
The idea here is to get Windows' userspace infrastructure to allocate
whatever space it needs for MapViewOfFileEx() before we release the
locked-down space that we want to map the shared memory block into.
This is a fairly brute-force attempt, and would likely (for example)
fail with large shared memory on 32-bit Windows. We could perhaps
ameliorate that by mapping only part of the shared memory block in
this way, but for the moment I just want to see if this approach
will fix dory's problem.
Discussion: https://postgr.es/m/25495.1524517820@sss.pgh.pa.us
Rather than elog'ing immediately, push the map data into a preallocated
StringInfo. Perhaps this will prevent some of the mid-operation
allocations that are evidently happening now.
Discussion: https://postgr.es/m/25495.1524517820@sss.pgh.pa.us
This code is evidently allocating memory and thus confusing matters
even more. Let's see whether we can learn anything with
just VirtualQuery.
Discussion: https://postgr.es/m/25495.1524517820@sss.pgh.pa.us
This morning's results from buildfarm member dory make it pretty
clear that something is getting mapped into the just-freed space,
but not what that something is. Replace my minimalistic probes
with a full dump of the process address space and module space,
based on Noah's work at
<20170403065106.GA2624300%40tornado.leadboat.com>
This is all (probably) to get reverted once we have fixed the
problem, but for now we need information.
Discussion: https://postgr.es/m/25495.1524517820@sss.pgh.pa.us
After some thought about the info captured so far, it seems possible
that MapViewOfFileEx is itself causing some DLL to get loaded into
the space just freed by VirtualFree. The previous commit here didn't
capture enough info to really prove the case for that, so let's add
one more VirtualQuery in between those steps. Also, be sure to
capture the post-Map state before we emit any log entries, just in
case elog() is invoking some code not previously loaded.
Discussion: https://postgr.es/m/25495.1524517820@sss.pgh.pa.us
Add some debug printouts focused on the idea that MapViewOfFileEx might
be rounding its virtual memory allocation up more than we expect (and,
in particular, more than VirtualAllocEx does).
Once we've seen what this reports in one of the failures on buildfarm
members dory or jacana, we might revert this ... or perhaps just
decrease the log level.
Discussion: https://postgr.es/m/25495.1524517820@sss.pgh.pa.us
Add support for huge pages (called large pages on Windows) to the
Windows build.
This (probably) breaks compatibility with Windows versions prior to
Windows 2003 or Windows Vista.
Authors: Takayuki Tsunakawa and Thomas Munro
Reviewed by: Magnus Hagander, Amit Kapila
Change pg_bsd_indent to follow upstream rules for placement of comments
to the right of code, and remove pgindent hack that caused comments
following #endif to not obey the general rule.
Commit e3860ffa4d wasn't actually using
the published version of pg_bsd_indent, but a hacked-up version that
tried to minimize the amount of movement of comments to the right of
code. The situation of interest is where such a comment has to be
moved to the right of its default placement at column 33 because there's
code there. BSD indent has always moved right in units of tab stops
in such cases --- but in the previous incarnation, indent was working
in 8-space tab stops, while now it knows we use 4-space tabs. So the
net result is that in about half the cases, such comments are placed
one tab stop left of before. This is better all around: it leaves
more room on the line for comment text, and it means that in such
cases the comment uniformly starts at the next 4-space tab stop after
the code, rather than sometimes one and sometimes two tabs after.
Also, ensure that comments following #endif are indented the same
as comments following other preprocessor commands such as #else.
That inconsistency turns out to have been self-inflicted damage
from a poorly-thought-through post-indent "fixup" in pgindent.
This patch is much less interesting than the first round of indent
changes, but also bulkier, so I thought it best to separate the effects.
Discussion: https://postgr.es/m/E1dAmxK-0006EE-1r@gemulon.postgresql.org
Discussion: https://postgr.es/m/30527.1495162840@sss.pgh.pa.us
Postmaster child processes that aren't supposed to be attached to shared
memory were not bothering to close the shared memory mapping handle they
inherit from the postmaster process. That's mostly harmless, since the
handle vanishes anyway when the child process exits -- but the syslogger
process, if used, doesn't get killed and restarted during recovery from a
backend crash. That meant that Windows doesn't see the shared memory
mapping as becoming free, so it doesn't delete it and the postmaster is
unable to create a new one, resulting in failure to recover from crashes
whenever logging_collector is turned on.
Per report from Dmitry Vasilyev. It's a bit astonishing that we'd not
figured this out long ago, since it's been broken from the very beginnings
of out native Windows support; probably some previously-unexplained trouble
reports trace to this.
A secondary problem is that on Cygwin (perhaps only in older versions?),
exec() may not detach from the shared memory segment after all, in which
case these child processes did remain attached to shared memory, posing
the risk of an unexpected shared memory clobber if they went off the rails
somehow. That may be a long-gone bug, but we can deal with it now if it's
still live, by detaching within the infrastructure introduced here to deal
with closing the handle.
Back-patch to all supported branches.
Tom Lane and Amit Kapila
Instead of storing the ID of the dynamic shared memory control
segment in a file within the data directory, store it in the main
control segment. This avoids a number of nasty corner cases,
most seriously that doing an online backup and then using it on
the same machine (e.g. to fire up a standby) would result in the
standby clobbering all of the master's dynamic shared memory
segments.
Per complaints from Heikki Linnakangas, Fujii Masao, and Tom
Lane.
This patch adds an option, huge_tlb_pages, which allows requesting the
shared memory segment to be allocated using huge pages, by using the
MAP_HUGETLB flag in mmap(). This can improve performance.
The default is 'try', which means that we will attempt using huge pages,
and fall back to non-huge pages if it doesn't work. Currently, only Linux
has MAP_HUGETLB. On other platforms, the default 'try' behaves the same as
'off'.
In the passing, don't try to round the mmap() size to a multiple of
pagesize. mmap() doesn't require that, and there's no particular reason for
PostgreSQL to do that either. When using MAP_HUGETLB, however, round the
request size up to nearest 2MB boundary. This is to work around a bug in
some Linux kernel versions, but also to avoid wasting memory, because the
kernel will round the size up anyway.
Many people were involved in writing this patch, including Christian Kruse,
Richard Poole, Abhijit Menon-Sen, reviewed by Peter Geoghegan, Andres Freund
and me.
Since C99, it's been standard for printf and friends to accept a "z" size
modifier, meaning "whatever size size_t has". Up to now we've generally
dealt with printing size_t values by explicitly casting them to unsigned
long and using the "l" modifier; but this is really the wrong thing on
platforms where pointers are wider than longs (such as Win64). So let's
start using "z" instead. To ensure we can do that on all platforms, teach
src/port/snprintf.c to understand "z", and add a configure test to force
use of that implementation when the platform's version doesn't handle "z".
Having done that, modify a bunch of places that were using the
unsigned-long hack to use "z" instead. This patch doesn't pretend to have
gotten everyplace that could benefit, but it catches many of them. I made
an effort in particular to ensure that all uses of the same error message
text were updated together, so as not to increase the number of
translatable strings.
It's possible that this change will result in format-string warnings from
pre-C99 compilers. We might have to reconsider if there are any popular
compilers that will warn about this; but let's start by seeing what the
buildfarm thinks.
Andres Freund, with a little additional work by me
that memory allocated by starting third party DLLs doesn't end up
conflicting with it.
Hopefully this solves the long-time issue with "could not reattach
to shared memory" errors on Win32.
Patch from Tsutomu Yamada and me, based on idea from Trevor Talbot.
it fails because the shared memory segment already exists. This
means it can take up to 10 seconds before it reports the error
if it *does* exist, but hopefully it will make the system capable
of restarting even when the server is under high load.
to make sure that the error code is reset, as a precaution in
case the API doesn't properly reset it on success. This could
be necessary, since we check the error value even if the function
doesn't fail for specific success cases.
in the Global\ namespace, because it caused permission errors on
a lot of platforms.
We need to come up with something better for 8.4, but for now
revert to the pre-8.3.4 behaviour.
Noah Misch