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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2012-05-14 16:11:59 -0400 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2012-05-14 16:12:28 -0400 |
| commit | e42a21b9e6c9b9e6346a34b62628d48ff2fc6ddf (patch) | |
| tree | 1d4c8483388c1ce744113596d457a4fd4f5cbe35 /src/backend/port/win32_latch.c | |
| parent | ff4628f37a1e700d1fe716d0c271f68d8aa1e4ea (diff) | |
Assert that WaitLatchOrSocket callers cannot wait only for writability.
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.
Diffstat (limited to 'src/backend/port/win32_latch.c')
| -rw-r--r-- | src/backend/port/win32_latch.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/src/backend/port/win32_latch.c b/src/backend/port/win32_latch.c index 62800ad66f2..05b34269b5a 100644 --- a/src/backend/port/win32_latch.c +++ b/src/backend/port/win32_latch.c @@ -106,6 +106,8 @@ WaitLatchOrSocket(volatile Latch *latch, int wakeEvents, pgsocket sock, wakeEvents &= ~(WL_SOCKET_READABLE | WL_SOCKET_WRITEABLE); Assert(wakeEvents != 0); /* must have at least one wake event */ + /* Cannot specify WL_SOCKET_WRITEABLE without WL_SOCKET_READABLE */ + Assert((wakeEvents & (WL_SOCKET_READABLE | WL_SOCKET_WRITEABLE)) != WL_SOCKET_WRITEABLE); if ((wakeEvents & WL_LATCH_SET) && latch->owner_pid != MyProcPid) elog(ERROR, "cannot wait on a latch owned by another process"); |