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Prevent possible crash reading pg_stat_activity.
Also, avoid reading PGPROC's wait_event field twice, once for the wait event and again for the wait_event_type, because the value might change in the middle. Petr Jelinek and Robert Haas
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36f69faeff
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c4a586c486
@ -27,6 +27,8 @@
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#include "utils/inet.h"
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#include "utils/timestamp.h"
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#define UINT32_ACCESS_ONCE(var) ((uint32)(*((volatile uint32 *)&(var))))
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/* bogus ... these externs should be in a header file */
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extern Datum pg_stat_get_numscans(PG_FUNCTION_ARGS);
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extern Datum pg_stat_get_tuples_returned(PG_FUNCTION_ARGS);
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@ -783,13 +785,26 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
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values[5] = CStringGetTextDatum(beentry->st_activity);
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proc = BackendPidGetProc(beentry->st_procpid);
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wait_event_type = pgstat_get_wait_event_type(proc->wait_event_info);
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if (proc != NULL)
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{
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uint32 raw_wait_event;
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raw_wait_event = UINT32_ACCESS_ONCE(proc->wait_event_info);
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wait_event_type = pgstat_get_wait_event_type(raw_wait_event);
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wait_event = pgstat_get_wait_event(raw_wait_event);
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}
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else
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{
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wait_event_type = NULL;
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wait_event = NULL;
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}
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if (wait_event_type)
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values[6] = CStringGetTextDatum(wait_event_type);
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else
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nulls[6] = true;
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wait_event = pgstat_get_wait_event(proc->wait_event_info);
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if (wait_event)
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values[7] = CStringGetTextDatum(wait_event);
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else
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@ -984,17 +999,14 @@ pg_stat_get_backend_wait_event_type(PG_FUNCTION_ARGS)
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int32 beid = PG_GETARG_INT32(0);
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PgBackendStatus *beentry;
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PGPROC *proc;
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const char *wait_event_type;
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const char *wait_event_type = NULL;
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if ((beentry = pgstat_fetch_stat_beentry(beid)) == NULL)
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wait_event_type = "<backend information not available>";
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else if (!has_privs_of_role(GetUserId(), beentry->st_userid))
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wait_event_type = "<insufficient privilege>";
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else
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{
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proc = BackendPidGetProc(beentry->st_procpid);
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else if ((proc = BackendPidGetProc(beentry->st_procpid)) != NULL)
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wait_event_type = pgstat_get_wait_event_type(proc->wait_event_info);
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}
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if (!wait_event_type)
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PG_RETURN_NULL();
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@ -1008,17 +1020,14 @@ pg_stat_get_backend_wait_event(PG_FUNCTION_ARGS)
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int32 beid = PG_GETARG_INT32(0);
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PgBackendStatus *beentry;
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PGPROC *proc;
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const char *wait_event;
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const char *wait_event = NULL;
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if ((beentry = pgstat_fetch_stat_beentry(beid)) == NULL)
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wait_event = "<backend information not available>";
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else if (!has_privs_of_role(GetUserId(), beentry->st_userid))
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wait_event = "<insufficient privilege>";
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else
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{
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proc = BackendPidGetProc(beentry->st_procpid);
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else if ((proc = BackendPidGetProc(beentry->st_procpid)) != NULL)
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wait_event = pgstat_get_wait_event(proc->wait_event_info);
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}
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if (!wait_event)
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PG_RETURN_NULL();
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