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Commit3e51725

Browse files
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Avoid depending on non-POSIX behavior of fcntl(2).
The POSIX standard does not say that the success return value forfcntl(F_SETFD) and fcntl(F_SETFL) is zero; it says only that it's not -1.We had several calls that were making the stronger assumption. Adjustthem to test specifically for -1 for strict spec compliance.The standard further leaves open the possibility that the O_NONBLOCKflag bit is not the only active one in F_SETFL's argument. Formally,therefore, one ought to get the current flags with F_GETFL and storethem back with only the O_NONBLOCK bit changed when trying to changethe nonblock state. In port/noblock.c, we were doing the full pushupin pg_set_block but not in pg_set_noblock, which is just weird. Makeboth of them do it properly, since they have little business makingany assumptions about the socket they're handed. The other placeswhere we're issuing F_SETFL are working with FDs we just got frompipe(2), so it's reasonable to assume the FDs' properties are alldefault, so I didn't bother adding F_GETFL steps there.Also, while pg_set_block deserves some points for trying to do thingsright, somebody had decided that it'd be even better to cast fcntl'sthird argument to "long". Which is completely loony, because POSIXclearly says the third argument for an F_SETFL call is "int".Given the lack of field complaints, these missteps apparently are notof significance on any common platforms. But they're still wrong,so back-patch to all supported branches.Discussion:https://postgr.es/m/30882.1492800880@sss.pgh.pa.us
1 parent68e61ee commit3e51725

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4 files changed

+25
-8
lines changed

4 files changed

+25
-8
lines changed

‎src/backend/postmaster/postmaster.c

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -6263,7 +6263,7 @@ InitPostmasterDeathWatchHandle(void)
62636263
* write fd. That is taken care of in ClosePostmasterPorts().
62646264
*/
62656265
Assert(MyProcPid==PostmasterPid);
6266-
if (pipe(postmaster_alive_fds))
6266+
if (pipe(postmaster_alive_fds)<0)
62676267
ereport(FATAL,
62686268
(errcode_for_file_access(),
62696269
errmsg_internal("could not create pipe to monitor postmaster death: %m")));
@@ -6272,7 +6272,7 @@ InitPostmasterDeathWatchHandle(void)
62726272
* Set O_NONBLOCK to allow testing for the fd's presence with a read()
62736273
* call.
62746274
*/
6275-
if (fcntl(postmaster_alive_fds[POSTMASTER_FD_WATCH],F_SETFL,O_NONBLOCK))
6275+
if (fcntl(postmaster_alive_fds[POSTMASTER_FD_WATCH],F_SETFL,O_NONBLOCK)==-1)
62766276
ereport(FATAL,
62776277
(errcode_for_socket_access(),
62786278
errmsg_internal("could not set postmaster death monitoring pipe to nonblocking mode: %m")));

‎src/backend/storage/ipc/latch.c

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -169,9 +169,9 @@ InitializeLatchSupport(void)
169169
*/
170170
if (pipe(pipefd)<0)
171171
elog(FATAL,"pipe() failed: %m");
172-
if (fcntl(pipefd[0],F_SETFL,O_NONBLOCK)<0)
172+
if (fcntl(pipefd[0],F_SETFL,O_NONBLOCK)==-1)
173173
elog(FATAL,"fcntl() failed on read-end of self-pipe: %m");
174-
if (fcntl(pipefd[1],F_SETFL,O_NONBLOCK)<0)
174+
if (fcntl(pipefd[1],F_SETFL,O_NONBLOCK)==-1)
175175
elog(FATAL,"fcntl() failed on write-end of self-pipe: %m");
176176

177177
selfpipe_readfd=pipefd[0];

‎src/bin/pg_test_fsync/pg_test_fsync.c

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -7,6 +7,7 @@
77

88
#include<sys/stat.h>
99
#include<sys/time.h>
10+
#include<fcntl.h>
1011
#include<time.h>
1112
#include<unistd.h>
1213
#include<signal.h>

‎src/port/noblock.c

Lines changed: 20 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -1,7 +1,7 @@
11
/*-------------------------------------------------------------------------
22
*
33
* noblock.c
4-
* set a file descriptor as non-blocking
4+
* set a file descriptor asblocking ornon-blocking
55
*
66
* Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
77
* Portions Copyright (c) 1994, Regents of the University of California
@@ -17,11 +17,22 @@
1717
#include<fcntl.h>
1818

1919

20+
/*
21+
* Put socket into nonblock mode.
22+
* Returns true on success, false on failure.
23+
*/
2024
bool
2125
pg_set_noblock(pgsocketsock)
2226
{
2327
#if !defined(WIN32)
24-
return (fcntl(sock,F_SETFL,O_NONBLOCK)!=-1);
28+
intflags;
29+
30+
flags=fcntl(sock,F_GETFL);
31+
if (flags<0)
32+
return false;
33+
if (fcntl(sock,F_SETFL, (flags |O_NONBLOCK))==-1)
34+
return false;
35+
return true;
2536
#else
2637
unsigned longioctlsocket_ret=1;
2738

@@ -30,15 +41,20 @@ pg_set_noblock(pgsocket sock)
3041
#endif
3142
}
3243

33-
44+
/*
45+
* Put socket into blocking mode.
46+
* Returns true on success, false on failure.
47+
*/
3448
bool
3549
pg_set_block(pgsocketsock)
3650
{
3751
#if !defined(WIN32)
3852
intflags;
3953

4054
flags=fcntl(sock,F_GETFL);
41-
if (flags<0||fcntl(sock,F_SETFL, (long) (flags& ~O_NONBLOCK)))
55+
if (flags<0)
56+
return false;
57+
if (fcntl(sock,F_SETFL, (flags& ~O_NONBLOCK))==-1)
4258
return false;
4359
return true;
4460
#else

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