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Allow concurrent-safe open() and fopen() in frontend code for Windows

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PostgreSQL uses a custom wrapper for open() and fopen() which is
concurrent-safe, allowing multiple processes to open and work on the
same file.  This has a couple of advantages:
- pg_test_fsync does not handle O_DSYNC correctly otherwise, leading to
false claims that disks are unsafe.
- TAP tests can run into race conditions when a postmaster and pg_ctl
open postmaster.pid, fixing some random failures in the buildfam.

pg_upgrade is one frontend tool using workarounds to bypass file locking
issues with the log files it generates, however the interactions with
pg_ctl are proving to be tedious to get rid of, so this is left for
later.

Author: Laurenz Albe
Reviewed-by: Michael Paquier, Kuntal Ghosh
Discussion: https://postgr.es/m/1527846213.2475.31.camel@cybertec.at
Discussion: https://postgr.es/m/16922.1520722108@sss.pgh.pa.us
This commit is contained in:
Michael Paquier
2018-09-17 20:38:42 +09:00
parent bcbd159027
commit f02259fe93
5 changed files with 12 additions and 7 deletions
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4
src/common/file_utils.c
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@ -222,7 +222,7 @@ pre_sync_fname(const char *fname, bool isdir, const char *progname)
{
int fd;
fd = open(fname, O_RDONLY | PG_BINARY);
fd = open(fname, O_RDONLY | PG_BINARY, 0);
if (fd < 0)
{
@ -283,7 +283,7 @@ fsync_fname(const char *fname, bool isdir, const char *progname)
* unsupported operations, e.g. opening a directory under Windows), and
* logging others.
*/
fd = open(fname, flags);
fd = open(fname, flags, 0);
if (fd < 0)
{
if (errno == EACCES || (isdir && errno == EISDIR))