diff options
| author | Robert Haas <rhaas@postgresql.org> | 2016-09-20 12:04:41 -0400 |
|---|---|---|
| committer | Robert Haas <rhaas@postgresql.org> | 2016-09-20 12:12:36 -0400 |
| commit | c23b2523d3fcc09524e6720d7c2558ba1ee6c239 (patch) | |
| tree | 4e59a440f14fd04508bbaaacc6274bbd063184d1 | |
| parent | 476945c451d675cc31cd89bce202b775cef45a8e (diff) | |
Retry DSM control segment creation if Windows indicates access denied.
Otherwise, attempts to run multiple postmasters running on the same
machine may fail, because Windows sometimes returns ERROR_ACCESS_DENIED
rather than ERROR_ALREADY_EXISTS when there is an existing segment.
Hitting this bug is much more likely because of another defect not
fixed by this patch, namely that dsm_postmaster_startup() uses
random() which returns the same value every time. But that's not
a reason not to fix this.
Kyotaro Horiguchi and Amit Kapila, reviewed by Michael Paquier
Discussion: <CAA4eK1JyNdMeF-dgrpHozDecpDfsRZUtpCi+1AbtuEkfG3YooQ@mail.gmail.com>
| -rw-r--r-- | src/backend/storage/ipc/dsm_impl.c | 31 |
1 files changed, 18 insertions, 13 deletions
diff --git a/src/backend/storage/ipc/dsm_impl.c b/src/backend/storage/ipc/dsm_impl.c index 35969c4501d..ff72d045ea5 100644 --- a/src/backend/storage/ipc/dsm_impl.c +++ b/src/backend/storage/ipc/dsm_impl.c @@ -671,6 +671,7 @@ dsm_impl_windows(dsm_op op, dsm_handle handle, Size request_size, { DWORD size_high; DWORD size_low; + DWORD errcode; /* Shifts >= the width of the type are undefined. */ #ifdef _WIN64 @@ -686,27 +687,31 @@ dsm_impl_windows(dsm_op op, dsm_handle handle, Size request_size, size_high, /* Upper 32 bits of size */ size_low, /* Lower 32 bits of size */ name); + + errcode = GetLastError(); + if (errcode == ERROR_ALREADY_EXISTS || errcode == ERROR_ACCESS_DENIED) + { + /* + * On Windows, when the segment already exists, a handle for the + * existing segment is returned. We must close it before + * returning. However, if the existing segment is created by a + * service, then it returns ERROR_ACCESS_DENIED. We don't do + * _dosmaperr here, so errno won't be modified. + */ + if (hmap) + CloseHandle(hmap); + return false; + } + if (!hmap) { - _dosmaperr(GetLastError()); + _dosmaperr(errcode); ereport(elevel, (errcode_for_dynamic_shared_memory(), errmsg("could not create shared memory segment \"%s\": %m", name))); return false; } - _dosmaperr(GetLastError()); - if (errno == EEXIST) - { - /* - * On Windows, when the segment already exists, a handle for the - * existing segment is returned. We must close it before - * returning. We don't do _dosmaperr here, so errno won't be - * modified. - */ - CloseHandle(hmap); - return false; - } } else { |