diff options
Diffstat (limited to 'src/backend/postmaster/pgstat.c')
| -rw-r--r-- | src/backend/postmaster/pgstat.c | 73 |
1 files changed, 71 insertions, 2 deletions
diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c index 44956c15b5a..ba64f2395c0 100644 --- a/src/backend/postmaster/pgstat.c +++ b/src/backend/postmaster/pgstat.c @@ -58,6 +58,7 @@ #include "storage/pg_shmem.h" #include "storage/pmsignal.h" #include "storage/procsignal.h" +#include "utils/ascii.h" #include "utils/guc.h" #include "utils/memutils.h" #include "utils/ps_status.h" @@ -2228,6 +2229,7 @@ static PgBackendStatus *MyBEEntry = NULL; static char *BackendClientHostnameBuffer = NULL; static char *BackendAppnameBuffer = NULL; static char *BackendActivityBuffer = NULL; +static Size BackendActivityBufferSize = 0; /* @@ -2310,9 +2312,12 @@ CreateSharedBackendStatus(void) } /* Create or attach to the shared activity buffer */ - size = mul_size(pgstat_track_activity_query_size, MaxBackends); + BackendActivityBufferSize = mul_size(pgstat_track_activity_query_size, + MaxBackends); BackendActivityBuffer = (char *) - ShmemInitStruct("Backend Activity Buffer", size, &found); + ShmemInitStruct("Backend Activity Buffer", + BackendActivityBufferSize, + &found); if (!found) { @@ -2751,6 +2756,70 @@ pgstat_get_backend_current_activity(int pid, bool checkUser) return "<backend information not available>"; } +/* ---------- + * pgstat_get_crashed_backend_activity() - + * + * Return a string representing the current activity of the backend with + * the specified PID. Like the function above, but reads shared memory with + * the expectation that it may be corrupt. Returns either a pointer to a + * constant string, or writes into the 'buffer' argument and returns it. + * + * This function is only intended to be used by postmaster to report the + * query that crashed the backend. In particular, no attempt is made to + * follow the correct concurrency protocol when accessing the + * BackendStatusArray. But that's OK, in the worst case we'll return a + * corrupted message. We also must take care not to trip on ereport(ERROR). + * + * Note: return strings for special cases match pg_stat_get_backend_activity. + * ---------- + */ +const char * +pgstat_get_crashed_backend_activity(int pid, char *buffer, + int len) +{ + volatile PgBackendStatus *beentry; + int i; + + beentry = BackendStatusArray; + for (i = 1; i <= MaxBackends; i++) + { + if (beentry->st_procpid == pid) + { + /* Read pointer just once, so it can't change after validation */ + const char *activity = beentry->st_activity; + const char *activity_last; + + /* + * We can't access activity pointer before we verify that it + * falls into BackendActivityBuffer. To make sure that the entire + * string including its ending is contained within the buffer, + * we subtract one activity length from it. + */ + activity_last = BackendActivityBuffer + BackendActivityBufferSize + - pgstat_track_activity_query_size; + + if (activity < BackendActivityBuffer || + activity > activity_last) + return "<command string corrupt>"; + + if (*(activity) == '\0') + return "<command string empty>"; + + /* + * Copy only ASCII-safe characters so we don't run into encoding + * problems when reporting the message. + */ + ascii_safe_strncpy(buffer, activity, len); + + return buffer; + } + + beentry++; + } + + /* PID not found */ + return "<backend information not available>"; +} /* ------------------------------------------------------------ * Local support functions follow |