New test: reveals race (found by Volker) when open occurs during transaction commit.

[ccan] / ccan / tdb / test / external-transaction.c

diff --git a/ccan/tdb/test/external-transaction.c b/ccan/tdb/test/external-transaction.c
index c03dbc49f6320afd386a5e9f89a2bad936034cf8..1211da9e76d5c1d54702f3725fc34e30eb8d9658 100644 (file)
--- a/ccan/tdb/test/external-transaction.c
+++ b/ccan/tdb/test/external-transaction.c
@@ -7,7 +7,9 @@
 #include <stdlib.h>
 #include <limits.h>
 #include <string.h>
+#include <errno.h>
 #include <ccan/tdb/tdb.h>
+#include <ccan/tap/tap.h>
 
 static volatile sig_atomic_t alarmed;
 static void do_alarm(int signum)
@@ -15,15 +17,22 @@ static void do_alarm(int signum)
        alarmed++;
 }
 
-static int do_transaction(const char *name)
+static int do_operation(enum operation op, const char *name)
 {
        TDB_DATA k = { .dptr = (void *)"a", .dsize = 1 };
        TDB_DATA d = { .dptr = (void *)"b", .dsize = 1 };
-       struct tdb_context *tdb = tdb_open(name, 0, 0, O_RDWR, 0);
+       struct tdb_context *tdb;
 
+       tdb = tdb_open(name, 0, op == OPEN_WITH_CLEAR_IF_FIRST ?
+                      TDB_CLEAR_IF_FIRST : TDB_DEFAULT, O_RDWR, 0);
        if (!tdb)
                return -1;
 
+       if (op == OPEN || op == OPEN_WITH_CLEAR_IF_FIRST) {
+               tdb_close(tdb);
+               return 0;
+       }
+
        alarmed = 0;
        tdb_setalarm_sigptr(tdb, &alarmed);
 
@@ -61,7 +70,7 @@ struct agent *prepare_external_agent(void)
        int pid;
        int command[2], response[2];
        struct sigaction act = { .sa_handler = do_alarm };
-       char name[PATH_MAX];
+       char name[1+PATH_MAX];
 
        if (pipe(command) != 0 || pipe(response) != 0)
                return NULL;
@@ -85,7 +94,9 @@ struct agent *prepare_external_agent(void)
        sigaction(SIGALRM, &act, NULL);
 
        while (read(command[0], name, sizeof(name)) != 0) {
-               int result = do_transaction(name);
+               int result;
+
+               result = do_operation(name[0], name+1);
                if (write(response[1], &result, sizeof(result))
                    != sizeof(result))
                        err(1, "Writing response");
@@ -93,13 +104,17 @@ struct agent *prepare_external_agent(void)
        exit(0);
 }
 
-/* Ask the external agent to try to do a transaction. */
-bool external_agent_transaction(struct agent *agent, const char *tdbname)
+/* Ask the external agent to try to do an operation. */
+bool external_agent_operation(struct agent *agent,
+                             enum operation op, const char *tdbname)
 {
        int res;
+       char string[1 + strlen(tdbname) + 1];
 
-       if (write(agent->cmdfd, tdbname, strlen(tdbname)+1)
-           != strlen(tdbname)+1)
+       string[0] = op;
+       strcpy(string+1, tdbname);
+
+       if (write(agent->cmdfd, string, sizeof(string)) != sizeof(string))
                err(1, "Writing to agent");
 
        if (read(agent->responsefd, &res, sizeof(res)) != sizeof(res))
@@ -110,3 +125,41 @@ bool external_agent_transaction(struct agent *agent, const char *tdbname)
 
        return res;
 }
+
+void external_agent_operation_start(struct agent *agent,
+                                   enum operation op, const char *tdbname)
+{
+       char string[1 + strlen(tdbname) + 1];
+
+       string[0] = op;
+       strcpy(string+1, tdbname);
+
+       if (write(agent->cmdfd, string, sizeof(string)) != sizeof(string))
+               err(1, "Writing to agent");
+}
+
+bool external_agent_operation_check(struct agent *agent, bool block, int *res)
+{
+       int flags = fcntl(agent->responsefd, F_GETFL);
+
+       if (block)
+               fcntl(agent->responsefd, F_SETFL, flags & ~O_NONBLOCK);
+       else
+               fcntl(agent->responsefd, F_SETFL, flags | O_NONBLOCK);
+
+       switch (read(agent->responsefd, res, sizeof(*res))) {
+       case sizeof(*res):
+               break;
+       case 0:
+               errx(1, "Agent died?");
+       default:
+               if (!block && (errno == EAGAIN || errno == EWOULDBLOCK))
+                       return false;
+               err(1, "%slocking reading from agent", block ? "B" : "Non-b");
+       }
+
+       if (*res > 1)
+               errx(1, "Agent returned %u\n", *res);
+
+       return true;
+}