From dbfa55f73aa32cb743b4d0d497fa8cea01863a6a Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Thu, 27 May 2010 19:20:06 +0000 Subject: [PATCH] Change ps_status.c to explicitly track the current logical length of ps_buffer. 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. --- src/backend/utils/misc/ps_status.c | 37 ++++++++++++------------------ 1 file changed, 15 insertions(+), 22 deletions(-) diff --git a/src/backend/utils/misc/ps_status.c b/src/backend/utils/misc/ps_status.c index cfc857de0a..224dab65b0 100644 --- a/src/backend/utils/misc/ps_status.c +++ b/src/backend/utils/misc/ps_status.c @@ -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; } -- 2.40.0