Changeset: 48fec04bccd1 for MonetDB
URL: http://dev.monetdb.org/hg/MonetDB?cmd=changeset;node=48fec04bccd1
Modified Files:
tools/merovingian/daemon/forkmserver.c
tools/merovingian/daemon/merovingian.c
tools/merovingian/daemon/merovingian.h
Branch: Jun2016
Log Message:
Fix race.
In logListener, only read from file descriptors that we added to the
list of file descriptors to read. If during the wait in select a file
descriptor is closed and the corresponding link in the list is freed,
and then a new link is added that happens to contain the same file
descriptor, we don't want to read from that one.
We do this by setting a flag that we're interested in the file
descriptor, and only reading from file descriptors whose flag is set.
See bug 4066, comment 29.
diffs (96 lines):
diff --git a/tools/merovingian/daemon/forkmserver.c
b/tools/merovingian/daemon/forkmserver.c
--- a/tools/merovingian/daemon/forkmserver.c
+++ b/tools/merovingian/daemon/forkmserver.c
@@ -350,6 +350,7 @@ forkMserver(char *database, sabdb** stat
dp->type = MEROFUN;
dp->pid = getpid();
dp->dbname = strdup(database);
+ dp->flag = 0;
pthread_mutex_unlock(&_mero_topdp_lock);
@@ -581,6 +582,7 @@ forkMserver(char *database, sabdb** stat
dp->type = MERODB;
dp->pid = pid;
dp->dbname = strdup(database);
+ dp->flag = 0;
pthread_mutex_unlock(&_mero_topdp_lock);
diff --git a/tools/merovingian/daemon/merovingian.c
b/tools/merovingian/daemon/merovingian.c
--- a/tools/merovingian/daemon/merovingian.c
+++ b/tools/merovingian/daemon/merovingian.c
@@ -199,6 +199,7 @@ logListener(void *x)
FD_SET(w->err, &readfds);
if (nfds < w->err)
nfds = w->err;
+ w->flag |= 1;
w = w->next;
}
@@ -216,12 +217,16 @@ logListener(void *x)
w = d;
while (w != NULL) {
- if (FD_ISSET(w->out, &readfds) != 0)
- logFD(w->out, "MSG", w->dbname,
- (long long int)w->pid,
_mero_logfile);
- if (w->err != w->out && FD_ISSET(w->err, &readfds) != 0)
- logFD(w->err, "ERR", w->dbname,
- (long long int)w->pid,
_mero_logfile);
+ /* only look at records we've added in the previous
loop */
+ if (w->flag & 1) {
+ if (FD_ISSET(w->out, &readfds) != 0)
+ logFD(w->out, "MSG", w->dbname,
+ (long long int)w->pid,
_mero_logfile);
+ if (w->err != w->out && FD_ISSET(w->err,
&readfds) != 0)
+ logFD(w->err, "ERR", w->dbname,
+ (long long int)w->pid,
_mero_logfile);
+ w->flag &= ~1;
+ }
w = w->next;
}
@@ -625,6 +630,7 @@ main(int argc, char *argv[])
_mero_topdp->pid = 0;
_mero_topdp->type = MERO;
_mero_topdp->dbname = NULL;
+ _mero_topdp->flag = 0;
/* where should our msg output go to? */
p = getConfVal(_mero_props, "logfile");
@@ -667,6 +673,7 @@ main(int argc, char *argv[])
d->pid = getpid();
d->type = MERO;
d->dbname = "merovingian";
+ d->flag = 0;
/* separate entry for the neighbour discovery service */
d = d->next = &dpdisc;
@@ -688,6 +695,7 @@ main(int argc, char *argv[])
d->type = MERO;
d->dbname = "discovery";
d->next = NULL;
+ d->flag = 0;
/* separate entry for the control runner */
d = d->next = &dpcont;
@@ -709,6 +717,7 @@ main(int argc, char *argv[])
d->type = MERO;
d->dbname = "control";
d->next = NULL;
+ d->flag = 0;
/* allow a thread to relock this mutex */
pthread_mutexattr_init(&mta);
diff --git a/tools/merovingian/daemon/merovingian.h
b/tools/merovingian/daemon/merovingian.h
--- a/tools/merovingian/daemon/merovingian.h
+++ b/tools/merovingian/daemon/merovingian.h
@@ -57,6 +57,7 @@ typedef struct _dpair {
int out; /* where to read stdout messages from */
int err; /* where to read stderr messages from */
mtype type; /* type of process */
+ short flag; /* flag internal to logListener */
pid_t pid; /* this process' id */
char *dbname; /* the database that this server serves */
struct _dpair* next;
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