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Change ps_status.c to explicitly track the current logical length of ps_buffer.

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This saves cycles in get_ps_display() on many popular platforms, and more
importantly ensures that get_ps_display() will correctly return an empty
string if init_ps_display() hasn't been called yet.  Per trouble report
from Ray Stell, in which log_line_prefix %i produced junk early in backend
startup.

Back-patch to 8.0.  7.4 doesn't have %i and its version of get_ps_display()
makes no pretense of avoiding pad junk anyhow.
This commit is contained in:
Tom Lane 2010-05-27 19:20:06 +00:00
parent b5285c19eb
commit dbfa55f73a
1 changed files with 15 additions and 22 deletions
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37
src/backend/utils/misc/ps_status.c
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@ -5,7 +5,7 @@
* to contain some useful information. Mechanism differs wildly across
* platforms.
*
* $PostgreSQL: pgsql/src/backend/utils/misc/ps_status.c,v 1.26.2.1 2005/11/22 18:23:25 momjian Exp $
* $PostgreSQL: pgsql/src/backend/utils/misc/ps_status.c,v 1.26.2.2 2010/05/27 19:20:06 tgl Exp $
*
* Copyright (c) 2000-2005, PostgreSQL Global Development Group
* various details abducted from various places
@ -88,8 +88,11 @@ static const size_t ps_buffer_size = PS_BUFFER_SIZE;
#else /* PS_USE_CLOBBER_ARGV */
static char *ps_buffer; /* will point to argv area */
static size_t ps_buffer_size; /* space determined at run time */
static size_t last_status_len; /* use to minimize length of clobber */
#endif /* PS_USE_CLOBBER_ARGV */
static size_t ps_buffer_cur_len; /* nominal strlen(ps_buffer) */
static size_t ps_buffer_fixed_size; /* size of the constant prefix */
/* save the original argv[] location here */
@ -174,7 +177,7 @@ save_ps_display_args(int argc, char **argv)
}
ps_buffer = argv[0];
ps_buffer_size = end_of_area - argv[0];
last_status_len = ps_buffer_size = end_of_area - argv[0];
/*
* move the environment out of the way
@ -290,7 +293,7 @@ init_ps_display(const char *username, const char *dbname,
username, dbname, host_info);
#endif
ps_buffer_fixed_size = strlen(ps_buffer);
ps_buffer_cur_len = ps_buffer_fixed_size = strlen(ps_buffer);
#ifdef WIN32
pgwin32_update_ident(ps_buffer);
@ -321,6 +324,7 @@ set_ps_display(const char *activity)
/* Update ps_buffer to contain both fixed part and activity */
StrNCpy(ps_buffer + ps_buffer_fixed_size, activity,
ps_buffer_size - ps_buffer_fixed_size);
ps_buffer_cur_len = strlen(ps_buffer);
/* Transmit new setting to kernel, if necessary */
@ -333,7 +337,7 @@ set_ps_display(const char *activity)
union pstun pst;
pst.pst_command = ps_buffer;
pstat(PSTAT_SETCMD, pst, strlen(ps_buffer), 0, 0);
pstat(PSTAT_SETCMD, pst, ps_buffer_cur_len, 0, 0);
}
#endif /* PS_USE_PSTAT */
@ -343,13 +347,11 @@ set_ps_display(const char *activity)
#endif /* PS_USE_PS_STRINGS */
#ifdef PS_USE_CLOBBER_ARGV
{
int buflen;
/* pad unused memory */
buflen = strlen(ps_buffer);
MemSet(ps_buffer + buflen, PS_PADDING, ps_buffer_size - buflen);
}
/* 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 */
#ifdef WIN32
@ -369,24 +371,15 @@ const char *
get_ps_display(int *displen)
{
#ifdef PS_USE_CLOBBER_ARGV
size_t offset;
/* If ps_buffer is a pointer, it might still be null */
if (!ps_buffer)
{
*displen = 0;
return "";
}
/* Remove any trailing spaces to offset the effect of PS_PADDING */
offset = ps_buffer_size;
while (offset > ps_buffer_fixed_size && ps_buffer[offset - 1] == PS_PADDING)
offset--;
*displen = offset - ps_buffer_fixed_size;
#else
*displen = strlen(ps_buffer + ps_buffer_fixed_size);
#endif
*displen = (int) (ps_buffer_cur_len - ps_buffer_fixed_size);
return ps_buffer + ps_buffer_fixed_size;
}