Thread: ps buffer is incorrectly padded on the (latest) OS X
Hi, I always wondered why ps ax|grep postgres shows several extra blank lines after the process name, i.e. 972 ?? Ss 0:00.69 postgres: writer process 973 ?? Ss 0:00.51 postgres: wal writer process (I put newlines instead of spaces there). By looking into the code I've found this part of set_ps_display: #ifdef PS_USE_CLOBBER_ARGV/* pad unused memory; need only clobber remainder of old status string */if (last_status_len >ps_buffer_cur_len) MemSet(ps_buffer + ps_buffer_cur_len, PS_PADDING, last_status_len - ps_buffer_cur_len);last_status_len= ps_buffer_cur_len; #endif /* PS_USE_CLOBBER_ARGV */ PS_PADDING padding on __darwin__ is set to ' '. Apparently this doesn't work correctly with OS X 10.6. After I changed the define to use '\0' on darwin extra blank likes (actually consisting of hundreds of spaces without a line break) disappeared. The one-liner change follows: === diff --git a/src/backend/utils/misc/ps_status.c b/src/backend/utils/misc/ps_status.c index f27a52f..c2ddf33 100644 --- a/src/backend/utils/misc/ps_status.c +++ b/src/backend/utils/misc/ps_status.c @@ -76,7 +76,7 @@ bool update_process_title = true;/* Different systems want the buffer padded differently */ -#if defined(_AIX) || defined(__linux__) || defined(__svr4__) +#if defined(_AIX) || defined(__linux__) || defined(__svr4__) || defined(__darwin__)#define PS_PADDING '\0'#else#define PS_PADDING' ' === I don't have different OS X versions to test, so I'm not sure whether 10.5 or below are also affected. Also, the patch should specifically check for 10.6, though I don't know how to distinguish between different OS X versions in postgres sources (any suggestions?). Regards, -- Alexey Klyukin http://www.CommandPrompt.com/ The PostgreSQL Company - Command Prompt, Inc
Alexey Klyukin <alexk@commandprompt.com> writes:
> I always wondered why ps ax|grep postgres shows several extra blank lines
> after the process name, i.e.
AFAIR it's always done that on OSX. I thought we'd tried the '\0'
padding way back when and it didn't work nicely, but maybe Apple fixed
that.
regards, tom lane
I wrote:
> Alexey Klyukin <alexk@commandprompt.com> writes:
>> I always wondered why ps ax|grep postgres shows several extra blank lines
>> after the process name, i.e.
> AFAIR it's always done that on OSX. I thought we'd tried the '\0'
> padding way back when and it didn't work nicely, but maybe Apple fixed
> that.
I tried this on a PPC Mac running 10.4.11, which is the oldest Mac OS
I have handy at the moment. It worked fine. The existing coding in
ps_status.c dates from late 2001, which means that it was first tested
against OS X 10.1, and most likely we have not rechecked the question
of what PS_PADDING value to use since then. My guess is that Apple
must have changed this in OS X 10.2 or 10.3, because the userland
Unix utilities were pretty well settled after that.
So I think we could definitely apply this change to HEAD/9.0, and I'm
strongly tempted to back-patch further than that. Does anybody think
that any pre-10.4 OS X versions are still in use, or would be likely
to receive Postgres updates if they do exist?
regards, tom lane
On Fri, Sep 3, 2010 at 7:09 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote: > I wrote: >> Alexey Klyukin <alexk@commandprompt.com> writes: >>> I always wondered why ps ax|grep postgres shows several extra blank lines >>> after the process name, i.e. > >> AFAIR it's always done that on OSX. I thought we'd tried the '\0' >> padding way back when and it didn't work nicely, but maybe Apple fixed >> that. > > I tried this on a PPC Mac running 10.4.11, which is the oldest Mac OS > I have handy at the moment. It worked fine. The existing coding in > ps_status.c dates from late 2001, which means that it was first tested > against OS X 10.1, and most likely we have not rechecked the question > of what PS_PADDING value to use since then. My guess is that Apple > must have changed this in OS X 10.2 or 10.3, because the userland > Unix utilities were pretty well settled after that. > > So I think we could definitely apply this change to HEAD/9.0, and I'm > strongly tempted to back-patch further than that. Does anybody think > that any pre-10.4 OS X versions are still in use, or would be likely > to receive Postgres updates if they do exist? I don't think we should back-patch this. It's not a bug fix, just a convenience. We already have enough trouble with people not believing that our minor releases are safe, and having non-critical stuff in the release notes does not help our case. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise Postgres Company
I wrote: > I tried this on a PPC Mac running 10.4.11, which is the oldest Mac OS > I have handy at the moment. It worked fine. The existing coding in > ps_status.c dates from late 2001, which means that it was first tested > against OS X 10.1, and most likely we have not rechecked the question > of what PS_PADDING value to use since then. My guess is that Apple > must have changed this in OS X 10.2 or 10.3, because the userland > Unix utilities were pretty well settled after that. Just for the archives' sake: I dug through the OS X source code archives and confirmed that this behavior changed at 10.3: compare getproclline in 10.2.8 http://www.opensource.apple.com/source/adv_cmds/adv_cmds-46/ps.tproj/print.c vs 10.3 http://www.opensource.apple.com/source/adv_cmds/adv_cmds-63/ps.tproj/print.c So we don't need a version check unless you're worried about somebody trying to run Postgres 9.x on OS X 10.2 (which was retired in 2003). regards, tom lane
On 04/09/10 22:41, Tom Lane wrote: > I wrote: >> I tried this on a PPC Mac running 10.4.11, which is the oldest Mac OS >> I have handy at the moment. It worked fine. The existing coding in >> ps_status.c dates from late 2001, which means that it was first tested >> against OS X 10.1, and most likely we have not rechecked the question >> of what PS_PADDING value to use since then. My guess is that Apple >> must have changed this in OS X 10.2 or 10.3, because the userland >> Unix utilities were pretty well settled after that. > > Just for the archives' sake: I dug through the OS X source code archives > and confirmed that this behavior changed at 10.3: compare getproclline > in 10.2.8 > http://www.opensource.apple.com/source/adv_cmds/adv_cmds-46/ps.tproj/print.c > vs 10.3 > http://www.opensource.apple.com/source/adv_cmds/adv_cmds-63/ps.tproj/print.c > > So we don't need a version check unless you're worried about somebody > trying to run Postgres 9.x on OS X 10.2 (which was retired in 2003). What happens if someone does? Crash, or just wonky ps output? If it's the latter, seems safe to backpatch. -- Heikki Linnakangas EnterpriseDB http://www.enterprisedb.com
Heikki Linnakangas <heikki.linnakangas@enterprisedb.com> writes:
> On 04/09/10 22:41, Tom Lane wrote:
>> So we don't need a version check unless you're worried about somebody
>> trying to run Postgres 9.x on OS X 10.2 (which was retired in 2003).
> What happens if someone does? Crash, or just wonky ps output? If it's
> the latter, seems safe to backpatch.
Wonky ps output. I don't recall exactly how wonky, but back in the day
it looked better blank-padded.
regards, tom lane