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* Combine win32 and unix latch implementations.Andres Freund2016-03-211-349/+0
| | | | | | | | | | | | | Previously latches for windows and unix had been implemented in different files. A later patch introduce an expanded wait infrastructure, keeping the implementation separate would introduce too much duplication. This basically just moves the functions, without too much change. The reason to keep this separate is that it allows blame to continue working a little less badly; and to make review a tiny bit easier. Discussion: 20160114143931.GG10941@awork2.anarazel.de
* Only clear latch self-pipe/event if there is a pending notification.Andres Freund2016-03-181-9/+10
| | | | | | | | | | | | | | | | This avoids a good number of, individually quite fast, system calls in scenarios with many quick queries. Besides the aesthetic benefit of seing fewer superflous system calls with strace, it also improves performance by ~2% measured by pgbench -M prepared -c 96 -j 8 -S (scale 100). Without having benchmarked it, this patch also adjust the windows code, as that makes it easier to unify the unix/windows codepaths in a later patch. There's little reason to diverge in behaviour between the platforms. Discussion: CA+TgmoYc1Zm+Szoc_Qbzi92z2c1vRHZmjhfPn5uC=w8bXv6Avg@mail.gmail.com Reviewed-By: Robert Haas
* Error out if waiting on socket readiness without a specified socket.Andres Freund2016-03-181-4/+5
| | | | | | | | | Previously we just ignored such an attempt, but that seems to serve no purpose but making things harder to debug. Discussion: 20160114143931.GG10941@awork2.anarazel.de 20151230173734.hx7jj2fnwyljfqek@alap3.anarazel.de Reviewed-By: Robert Haas
* Update copyright for 2016Bruce Momjian2016-01-021-1/+1
| | | | Backpatch certain files through 9.1
* Make WaitLatchOrSocket's timeout detection more robust.Tom Lane2015-07-181-3/+6
| | | | | | | | | | | | | | | | | | | | In the previous coding, timeout would be noticed and reported only when poll() or socket() returned zero (or the equivalent behavior on Windows). Ordinarily that should work well enough, but it seems conceivable that we could get into a state where poll() always returns a nonzero value --- for example, if it is noticing a condition on one of the file descriptors that we do not think is reason to exit the loop. If that happened, we'd be in a busy-wait loop that would fail to terminate even when the timeout expires. We can make this more robust at essentially no cost, by deciding to exit of our own accord if we compute a zero or negative time-remaining-to-wait. Previously the code noted this but just clamped the time-remaining to zero, expecting that we'd detect timeout on the next loop iteration. Back-patch to 9.2. While 9.1 had a version of WaitLatchOrSocket, it was primitive compared to later versions, and did not guarantee reliable detection of timeouts anyway. (Essentially, this is a refinement of commit 3e7fdcffd6f77187, which was back-patched only as far as 9.2.)
* pgindent run for 9.5Bruce Momjian2015-05-231-1/+1
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* Add barriers to the latch code.Andres Freund2015-01-131-0/+16
| | | | | | | | | | | | | | | | | | | | | Since their introduction latches have required barriers in SetLatch and ResetLatch - but when they were introduced there wasn't any barrier abstraction. Instead latches were documented to rely on the callsites to provide barrier semantics. Now that the barrier support looks halfway complete, add the necessary barriers to both latch implementations. Also remove a now superflous lock acquisition from syncrep.c and a superflous (and insufficient) barrier from freelist.c. There might be other cases that can now be simplified, but those are the only ones I've seen on a quick scan. We might want to backpatch this at some later point, but right now the barrier infrastructure in the backbranches isn't totally on par with master. Discussion: 20150112154026.GB2092@awork2.anarazel.de
* Allow latches to wait for socket writability without waiting for readability.Andres Freund2015-01-131-5/+10
| | | | | | | | | | | | | | | | | | | | | | | | | | | So far WaitLatchOrSocket() required to pass in WL_SOCKET_READABLE as that solely was used to indicate error conditions, like EOF. Waiting for WL_SOCKET_WRITEABLE would have meant to busy wait upon socket errors. Adjust the API to signal errors by returning the socket as readable, writable or both, depending on WL_SOCKET_READABLE/WL_SOCKET_WRITEABLE being specified. It would arguably be nicer to return WL_SOCKET_ERROR but that's not possible on platforms and would probably also result in more complex callsites. This previously had explicitly been forbidden in e42a21b9e6c9, as there was no strong use case at that point. We now are looking into making FE/BE communication use latches, so changing this makes sense. There also are some portability concerns because there cases of older platforms where select(2) is known to, in violation of POSIX, not return a socket as writable after the peer has closed it. So far the platforms where that's the case provide a working poll(2). If we find one where that's not the case, we'll need to add a workaround for that platform. Discussion: 20140927191243.GD5423@alap3.anarazel.de Reviewed-By: Heikki Linnakangas, Noah Misch
* Update copyright for 2015Bruce Momjian2015-01-061-1/+1
| | | | Backpatch certain files through 9.0
* pgindent run for 9.4Bruce Momjian2014-05-061-1/+1
| | | | | This includes removing tabs after periods in C comments, which was applied to back branches, so this change should not effect backpatching.
* Update copyright for 2014Bruce Momjian2014-01-071-1/+1
| | | | | Update all files in head, and files COPYRIGHT and legal.sgml in all back branches.
* Update copyrights for 2013Bruce Momjian2013-01-011-1/+1
| | | | | Fully update git head, and update back branches in ./COPYRIGHT and legal.sgml files.
* Assert that WaitLatch's timeout is not more than INT_MAX milliseconds.Tom Lane2012-11-181-1/+2
| | | | | | | | | | | | The behavior with larger values is unspecified by the Single Unix Spec. It appears that BSD-derived kernels report EINVAL, although Linux does not. If waiting for longer intervals is desired, the calling code has to do something to limit the delay; we can't portably fix it here since "long" may not be any wider than "int" in the first place. Part of response to bug #7670, though this change doesn't fix that (in fact, it converts the problem from an ERROR into an Assert failure). No back-patch since it's just an assertion addition.
* Fix WaitLatch() to return promptly when the requested timeout expires.Tom Lane2012-11-081-6/+31
| | | | | | | | | | | | | | | | If the sleep is interrupted by a signal, we must recompute the remaining time to wait; otherwise, a steady stream of non-wait-terminating interrupts could delay return from WaitLatch indefinitely. This has been shown to be a problem for the autovacuum launcher, and there may well be other places now or in the future with similar issues. So we'd better make the function robust, even though this'll add at least one gettimeofday call per wait. Back-patch to 9.2. We might eventually need to fix 9.1 as well, but the code is quite different there, and the usage of WaitLatch in 9.1 is so limited that it's not clearly important to do so. Reported and diagnosed by Jeff Janes, though I rewrote his patch rather heavily.
* Split up process latch initialization for more-fail-soft behavior.Tom Lane2012-10-141-0/+6
| | | | | | | | | | | | | | | | | | | | In the previous coding, new backend processes would attempt to create their self-pipe during the OwnLatch call in InitProcess. However, pipe creation could fail if the kernel is short of resources; and the system does not recover gracefully from a FATAL error right there, since we have armed the dead-man switch for this process and not yet set up the on_shmem_exit callback that would disarm it. The postmaster then forces an unnecessary database-wide crash and restart, as reported by Sean Chittenden. There are various ways we could rearrange the code to fix this, but the simplest and sanest seems to be to split out creation of the self-pipe into a new function InitializeLatchSupport, which must be called from a place where failure is allowed. For most processes that gets called in InitProcess or InitAuxiliaryProcess, but processes that don't call either but still use latches need their own calls. Back-patch to 9.1, which has only a part of the latch logic that 9.2 and HEAD have, but nonetheless includes this bug.
* Make walsender more responsive.Robert Haas2012-07-021-0/+4
| | | | | | | | | | | Per testing by Andres Freund, this improves replication performance and reduces replication latency and latency jitter. I was a bit concerned about moving more work into XLogInsert, but testing seems to show that it's not a problem in practice. Along the way, improve comments for WaitLatchOrSocket. Andres Freund. Review and stylistic cleanup by me.
* Run pgindent on 9.2 source tree in preparation for first 9.3Bruce Momjian2012-06-101-2/+3
| | | | commit-fest.
* Assert that WaitLatchOrSocket callers cannot wait only for writability.Tom Lane2012-05-141-0/+2
| | | | | | | | | | | | | Since we have chosen to report socket EOF and error conditions via the WL_SOCKET_READABLE flag bit, it's unsafe to wait only for WL_SOCKET_WRITEABLE; the caller would never be notified of the socket condition, and in some of these implementations WaitLatchOrSocket would busy-wait until something else happens. Add this restriction to the API specification, and add Asserts to check that callers don't try to do that. At some point we might want to consider adjusting the API to relax this restriction, but until we have an actual use case for waiting on a write-only socket, it seems premature to design a solution.
* Attempt to fix some issues in our Windows socket code.Tom Lane2012-05-131-7/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | Make sure WaitLatchOrSocket regards FD_CLOSE as a read-ready condition. We might want to tweak this further, but it was surely wrong as-is. Make pgwin32_waitforsinglesocket detach its private event object from the passed socket before returning. I suspect that failure to do so leads to race conditions when other code (such as WaitLatchOrSocket) attaches a different event object to the same socket. Moreover, the existing coding meant that repeated calls to pgwin32_waitforsinglesocket would perform ResetEvent on an event actively connected to a socket, which is rumored to be an unsafe practice; the WSAEventSelect documentation appears to recommend against this, though it does not say not to do it in so many words. Also, uniformly use the coding pattern "WSAEventSelect(s, NULL, 0)" to detach events from sockets, rather than passing the event in the second parameter. The WSAEventSelect documentation says that the second parameter is ignored if the third is 0, so theoretically this should make no difference. However, elsewhere on the same reference page the use of NULL in this context is recommended, and I have found suggestions on the net that some versions of Windows have bugs with a non-NULL second parameter in this usage. Some other mostly-cosmetic cleanup, such as using the right one of WSAGetLastError and GetLastError for reporting errors from these functions.
* Make WaitLatch's WL_POSTMASTER_DEATH result trustworthy; simplify callers.Tom Lane2012-05-101-2/+10
| | | | | | | | Per a suggestion from Peter Geoghegan, make WaitLatch responsible for verifying that the WL_POSTMASTER_DEATH bit it returns is truthful (by testing PostmasterIsAlive). Then simplify its callers, who no longer need to do that for themselves. Remove weasel wording about falsely-set result bits from WaitLatch's API contract.
* Improve Windows implementation of WaitLatch/WaitLatchOrSocket.Tom Lane2012-05-101-21/+39
| | | | | | | | | | Ensure that signal handlers are serviced before this function returns. This should make the behavior more like Unix. Also, add some more error checking, and make some other cosmetic improvements. No back-patch since it's not clear whether this is fixing any live bug that would affect 9.1. I'm more concerned about 9.2 anyway given our considerable recent expansions in the usage of WaitLatch.
* Update copyright notices for year 2012.Bruce Momjian2012-01-011-1/+1
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* Use consistent format for reporting GetLastError()Peter Eisentraut2011-08-231-6/+6
| | | | | | Use something like "error code %lu" for reporting GetLastError() values on Windows. Previously, a mix of different wordings and formats were in use.
* Measure WaitLatch's timeout parameter in milliseconds, not microseconds.Tom Lane2011-08-091-7/+3
| | | | | | | | | | | | The original definition had the problem that timeouts exceeding about 2100 seconds couldn't be specified on 32-bit machines. Milliseconds seem like sufficient resolution, and finer grain than that would be fantasy anyway on many platforms. Back-patch to 9.1 so that this aspect of the latch API won't change between 9.1 and later releases. Peter Geoghegan
* Documentation improvement and minor code cleanups for the latch facility.Tom Lane2011-08-091-24/+25
| | | | | | | | | | | | | | Improve the documentation around weak-memory-ordering risks, and do a pass of general editorialization on the comments in the latch code. Make the Windows latch code more like the Unix latch code where feasible; in particular provide the same Assert checks in both implementations. Fix poorly-placed WaitLatch call in syncrep.c. This patch resolves, for the moment, concerns around weak-memory-ordering bugs in latch-related code: we have documented the restrictions and checked that existing calls meet them. In 9.2 I hope that we will install suitable memory barrier instructions in SetLatch/ResetLatch, so that their callers don't need to be quite so careful.
* Replace printf format %i by %dPeter Eisentraut2011-07-261-1/+1
| | | | | They are identical, but the overwhelming majority of the code uses %d, so standardize on that.
* Silence compiler warning about uninitialized variable.Andrew Dunstan2011-07-251-1/+1
| | | | | It is set correctly on the only path that uses it, but the compiler can't know that.
* Introduce a pipe between postmaster and each backend, which can be used toHeikki Linnakangas2011-07-081-27/+71
| | | | | | | | | | | | | | | | | | | | | | | | | detect postmaster death. Postmaster keeps the write-end of the pipe open, so when it dies, children get EOF in the read-end. That can conveniently be waited for in select(), which allows eliminating some of the polling loops that check for postmaster death. This patch doesn't yet change all the loops to use the new mechanism, expect a follow-on patch to do that. This changes the interface to WaitLatch, so that it takes as argument a bitmask of events that it waits for. Possible events are latch set, timeout, postmaster death, and socket becoming readable or writeable. The pipe method behaves slightly differently from the kill() method previously used in PostmasterIsAlive() in the case that postmaster has died, but its parent has not yet read its exit code with waitpid(). The pipe returns EOF as soon as the process dies, but kill() continues to return true until waitpid() has been called (IOW while the process is a zombie). Because of that, change PostmasterIsAlive() to use the pipe too, otherwise WaitLatch() would return immediately with WL_POSTMASTER_DEATH, while PostmasterIsAlive() would claim it's still alive. That could easily lead to busy-waiting while postmaster is in zombie state. Peter Geoghegan with further changes by me, reviewed by Fujii Masao and Florian Pflug.
* Pgindent run before 9.1 beta2.Bruce Momjian2011-06-091-1/+1
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* Silence a few compiler warnings from gcc on MinGW.Andrew Dunstan2011-04-231-2/+2
| | | | | | | Most of these cast DWORD to int or unsigned int for printf type handling. This is safe even on 64 bit architectures because a DWORD is always 32 bits. In one case a variable is initialised to keep the compiler happy.
* pgindent run before PG 9.1 beta 1.Bruce Momjian2011-04-101-14/+14
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* Automatically terminate replication connections that are idle for moreHeikki Linnakangas2011-03-301-6/+24
| | | | | | | | | than replication_timeout (a new GUC) milliseconds. The TCP timeout is often too long, you want the master to notice a dead connection much sooner. People complained about that in 9.0 too, but with synchronous replication it's even more important to notice dead connections promptly. Fujii Masao and Heikki Linnakangas
* Stamp copyrights for year 2011.Bruce Momjian2011-01-011-1/+1
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* Remove cvs keywords from all files.Magnus Hagander2010-09-201-1/+1
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* Simplify Windows implementation of latches. There's no need to keep aHeikki Linnakangas2010-09-151-117/+31
| | | | | | | | dynamic pool of event handles, we can permanently assign one for each shared latch. Thanks to that, we no longer need a separate shared memory block for latches, and we don't need to know in advance how many shared latches there is, so you no longer need to remember to update NumSharedLatches when you introduce a new latch to the system.
* Introduce latches. A latch is a boolean variable, with the capability toHeikki Linnakangas2010-09-111-0/+284
wait until it is set. Latches can be used to reliably wait until a signal arrives, which is hard otherwise because signals don't interrupt select() on some platforms, and even when they do, there's race conditions. On Unix, latches use the so called self-pipe trick under the covers to implement the sleep until the latch is set, without race conditions. On Windows, Windows events are used. Use the new latch abstraction to sleep in walsender, so that as soon as a transaction finishes, walsender is woken up to immediately send the WAL to the standby. This reduces the latency between master and standby, which is good. Preliminary work by Fujii Masao. The latch implementation is by me, with helpful comments from many people.
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