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From: Tom Lane <tgl@sss.pgh.pa.us>

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Making PQrequestCancel safe to call in a signal handler turned out to be
much easier than I feared.  So here are the diffs.

Some notes:
  * I modified the postmaster's packet "iodone" callback interface to allow
    the callback routine to return a continue-or-drop-connection return
    code; this was necessary to allow the connection to be closed after
    receiving a Cancel, rather than proceeding to launch a new backend...
    Being a neatnik, I also made the iodone proc have a typechecked
    parameter list.
  * I deleted all code I could find that had to do with OOB.
  * I made some edits to ensure that all signals mentioned in the code
    are referred to symbolically not by numbers ("SIGUSR2" not "2").
    I think Bruce may have already done at least some of the same edits;
    I hope that merging these patches is not too painful.
This commit is contained in:
Marc G. Fournier
1998-07-09 03:29:11 +00:00
parent 8bf61820f0
commit a0659e3e2c
20 changed files with 597 additions and 287 deletions
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50
src/interfaces/libpq/fe-exec.c
View File

@ -7,7 +7,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/interfaces/libpq/fe-exec.c,v 1.55 1998/07/03 04:24:13 momjian Exp $
* $Header: /cvsroot/pgsql/src/interfaces/libpq/fe-exec.c,v 1.56 1998/07/09 03:29:08 scrappy Exp $
*
*-------------------------------------------------------------------------
*/
@ -361,6 +361,16 @@ parseInput(PGconn *conn)
PGRES_EMPTY_QUERY);
conn->asyncStatus = PGASYNC_READY;
break;
case 'K': /* secret key data from the backend */
/* This is expected only during backend startup,
* but it's just as easy to handle it as part of the
* main loop. Save the data and continue processing.
*/
if (pqGetInt(&(conn->be_pid), 4, conn))
return;
if (pqGetInt(&(conn->be_key), 4, conn))
return;
break;
case 'N': /* notices from the backend */
if (getNotice(conn))
return;
@ -761,44 +771,6 @@ PQexec(PGconn *conn, const char *query)
}
/*
* Attempt to request cancellation of the current operation.
*
* The return value is TRUE if the cancel request was successfully
* dispatched, FALSE if not (in which case errorMessage is set).
* Note: successful dispatch is no guarantee that there will be any effect at
* the backend. The application must read the operation result as usual.
*/
int
PQrequestCancel(PGconn *conn)
{
char msg[1];
if (!conn)
return FALSE;
if (conn->sock < 0)
{
sprintf(conn->errorMessage,
"PQrequestCancel() -- connection is not open\n");
return FALSE;
}
msg[0] = '\0';
if (send(conn->sock, msg, 1, MSG_OOB) < 0)
{
sprintf(conn->errorMessage,
"PQrequestCancel() -- couldn't send OOB data: errno=%d\n%s\n",
errno, strerror(errno));
return FALSE;
}
return TRUE;
}
/*
* Attempt to read a Notice response message.
* This is possible in several places, so we break it out as a subroutine.