The POSIX standard does not say that the success return value for
fcntl(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. Adjust
them to test specifically for -1 for strict spec compliance.
The standard further leaves open the possibility that the O_NONBLOCK
flag 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 store
them back with only the O_NONBLOCK bit changed when trying to change
the nonblock state. In port/noblock.c, we were doing the full pushup
in pg_set_block but not in pg_set_noblock, which is just weird. Make
both of them do it properly, since they have little business making
any assumptions about the socket they're handed. The other places
where we're issuing F_SETFL are working with FDs we just got from
pipe(2), so it's reasonable to assume the FDs' properties are all
default, so I didn't bother adding F_GETFL steps there.
Also, while pg_set_block deserves some points for trying to do things
right, somebody had decided that it'd be even better to cast fcntl's
third argument to "long". Which is completely loony, because POSIX
clearly says the third argument for an F_SETFL call is "int".
Given the lack of field complaints, these missteps apparently are not
of 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
The semantics of signal(2) are more variable than one could wish; in
particular, on strict-POSIX platforms the signal handler will be reset
to SIG_DFL when the signal is delivered. This demonstrably breaks
pg_test_fsync's use of SIGALRM. The other changes I made are not
absolutely necessary today, because the called handlers all exit the
program anyway. But it seems like a good general practice to use
pqsignal() exclusively in Postgres code, now that we have it available
everywhere.
Clarify the docs explaining what commit_delay does, and add a
recommendation about a useful value for it, namely half of the single-page
fsync time reported by pg_test_fsync. This is informed by testing of
the new-in-9.3 implementation of commit_delay; in prior versions it
was far harder to arrive at a useful setting.
In passing, do some wordsmithing and markup-fixing in the same general
area.
Also, change pg_test_fsync's default time-per-test from 2 seconds to 5.
The old value was about the minimum at which the results could be taken
seriously at all, and so seems a tad optimistic as a default.
Peter Geoghegan, reviewed by Noah Misch; some additional editing by me
Reduce #includes to minimum actually needed; in particular include
postgres_fe.h not postgres.h, so as to stop build failures on some
platforms.
Use get_progname() instead of hardwired program name; improve error
checking for command line syntax; bring error messages into line with
style guidelines; include strerror result in die() cases.
Un-break Windows build (I hope) by making the HAVE_FSYNC_WRITETHROUGH
code match the backend. Fix incorrect program help message. static-ize
all functions.
Actually rename the program, rather than just claiming we did. Hook it
into the build system. Get rid of useless dependency on libpq. Clean up
#include list and messy whitespace.
