trans.c : reworking of transaction interruptions

My two previous hacks related to this part
(8038190c7c4786e1c49494eea1b40cdddcbd5136 and
b15a5194d1a8485a2769560e49e6ff03e1862533) were caused by the lack of
understanding of a feature introduced a while ago:
Better control over CTRL-C interruptions -- do not leave the DB in an
inconsistent state (54008798efcc9646f622f6b052ecd83281d57cda).

Now I have been looking at this commit, and the added feature is indeed
interesting. The main problem I had with it is that it does a rather
unusual use of alpm_trans_release, which caused a few problems that I tried
to fix in a weird way. I think these problems were caused by the fact that
there weren't any difference between "interrupt transaction" and "release a
transaction which failed" actions from the alpm_trans_release POV.  So I
decided to add a new function instead, alpm_trans_interrupt, which is
called on Ctrl+C, and which only sets trans->state to STATE_INTERRUPTED so
that remove_commit and add_commit can exit cleanly at a safe moment. This
allowed me to revert my two previous hacks as well.

Also ensure we handle SIGINT correctly in all cases- if a transaction is
not ongoing, then we can free the transaction and exit quickly.

Signed-off-by: Chantry Xavier <shiningxc@gmail.com>
Signed-off-by: Dan McGee <dan@archlinux.org>

6 files changed, 39 insertions, 26 deletions

diff --git a/lib/libalpm/add.c b/lib/libalpm/add.c
index 3f9a2a85..98906879 100644
--- a/lib/libalpm/add.c
+++ b/lib/libalpm/add.c
@@ -905,7 +905,7 @@ int _alpm_add_commit(pmtrans_t *trans, pmdb_t *db)
 	/* loop through our package list adding/upgrading one at a time */
 	for(targ = trans->packages; targ; targ = targ->next) {
 		if(handle->trans->state == STATE_INTERRUPTED) {
-			break;
+			return(0);
 		}
 
 		pmpkg_t *newpkg = (pmpkg_t *)targ->data;
@@ -914,10 +914,8 @@ int _alpm_add_commit(pmtrans_t *trans, pmdb_t *db)
 	}
 
 	/* run ldconfig if it exists */
-	if(handle->trans->state != STATE_INTERRUPTED) {
-		_alpm_log(PM_LOG_DEBUG, "running \"ldconfig -r %s\"\n", handle->root);
-		_alpm_ldconfig(handle->root);
-	}
+	_alpm_log(PM_LOG_DEBUG, "running \"ldconfig -r %s\"\n", handle->root);
+	_alpm_ldconfig(handle->root);
 
 	return(0);
 }
diff --git a/lib/libalpm/alpm.h b/lib/libalpm/alpm.h
index 81137e6d..4a44cc76 100644
--- a/lib/libalpm/alpm.h
+++ b/lib/libalpm/alpm.h
@@ -335,6 +335,7 @@ int alpm_trans_sysupgrade(void);
 int alpm_trans_addtarget(char *target);
 int alpm_trans_prepare(alpm_list_t **data);
 int alpm_trans_commit(alpm_list_t **data);
+int alpm_trans_interrupt(void);
 int alpm_trans_release(void);
 
 /*
diff --git a/lib/libalpm/db.c b/lib/libalpm/db.c
index 61c74a77..b06a970c 100644
--- a/lib/libalpm/db.c
+++ b/lib/libalpm/db.c
@@ -111,8 +111,7 @@ int SYMEXPORT alpm_db_unregister_all(void)
 	/* Sanity checks */
 	ASSERT(handle != NULL, RET_ERR(PM_ERR_HANDLE_NULL, -1));
 	/* Do not unregister a database if a transaction is on-going */
-	ASSERT(handle->trans == NULL || handle->trans->state == STATE_INTERRUPTED,
-			RET_ERR(PM_ERR_TRANS_NOT_NULL, -1));
+	ASSERT(handle->trans == NULL, RET_ERR(PM_ERR_TRANS_NOT_NULL, -1));
 
 	/* close local database */
 	_alpm_db_unregister(handle->db_local);
@@ -142,8 +141,7 @@ int SYMEXPORT alpm_db_unregister(pmdb_t *db)
 	ASSERT(handle != NULL, RET_ERR(PM_ERR_HANDLE_NULL, -1));
 	ASSERT(db != NULL, RET_ERR(PM_ERR_WRONG_ARGS, -1));
 	/* Do not unregister a database if a transaction is on-going */
-	ASSERT(handle->trans == NULL || handle->trans->state == STATE_INTERRUPTED,
-			RET_ERR(PM_ERR_TRANS_NOT_NULL, -1));
+	ASSERT(handle->trans == NULL, RET_ERR(PM_ERR_TRANS_NOT_NULL, -1));
 
 	if(db == handle->db_local) {
 		handle->db_local = NULL;
diff --git a/lib/libalpm/remove.c b/lib/libalpm/remove.c
index 010e7ab6..fb5ddb92 100644
--- a/lib/libalpm/remove.c
+++ b/lib/libalpm/remove.c
@@ -280,7 +280,7 @@ int _alpm_remove_commit(pmtrans_t *trans, pmdb_t *db)
 		const char *pkgname = NULL;
 
 		if(handle->trans->state == STATE_INTERRUPTED) {
-			break;
+			return(0);
 		}
 
 		/* get the name now so we can use it after package is removed */
@@ -360,8 +360,7 @@ int _alpm_remove_commit(pmtrans_t *trans, pmdb_t *db)
 	}
 
 	/* run ldconfig if it exists */
-	if((trans->type != PM_TRANS_TYPE_REMOVEUPGRADE)
-			&& (handle->trans->state != STATE_INTERRUPTED)) {
+	if(trans->type != PM_TRANS_TYPE_REMOVEUPGRADE) {
 		_alpm_log(PM_LOG_DEBUG, "running \"ldconfig -r %s\"\n", handle->root);
 		_alpm_ldconfig(handle->root);
 	}
diff --git a/lib/libalpm/trans.c b/lib/libalpm/trans.c
index fe37a1f9..9eb27c30 100644
--- a/lib/libalpm/trans.c
+++ b/lib/libalpm/trans.c
@@ -165,13 +165,34 @@ int SYMEXPORT alpm_trans_commit(alpm_list_t **data)
 	return(_alpm_trans_commit(handle->trans, data));
 }
 
+/** Interrupt a transaction.
+ * @return 0 on success, -1 on error (pm_errno is set accordingly)
+ */
+int SYMEXPORT alpm_trans_interrupt()
+{
+	pmtrans_t *trans;
+
+	ALPM_LOG_FUNC;
+
+	/* Sanity checks */
+	ASSERT(handle != NULL, RET_ERR(PM_ERR_HANDLE_NULL, -1));
+
+	trans = handle->trans;
+	ASSERT(trans != NULL, RET_ERR(PM_ERR_TRANS_NULL, -1));
+	ASSERT(trans->state == STATE_COMMITING || trans->state == STATE_INTERRUPTED,
+			RET_ERR(PM_ERR_TRANS_TYPE, -1));
+
+	trans->state = STATE_INTERRUPTED;
+
+	return(0);
+}
+
 /** Release a transaction.
  * @return 0 on success, -1 on error (pm_errno is set accordingly)
  */
 int SYMEXPORT alpm_trans_release()
 {
 	pmtrans_t *trans;
-	int ret = 0;
 
 	ALPM_LOG_FUNC;
 
@@ -182,15 +203,6 @@ int SYMEXPORT alpm_trans_release()
 	ASSERT(trans != NULL, RET_ERR(PM_ERR_TRANS_NULL, -1));
 	ASSERT(trans->state != STATE_IDLE, RET_ERR(PM_ERR_TRANS_NULL, -1));
 
-	/* during a commit do not interrupt immediately, just after a target */
-	if(trans->state == STATE_COMMITING || trans->state == STATE_INTERRUPTED) {
-		if(trans->state == STATE_COMMITING) {
-			trans->state = STATE_INTERRUPTED;
-		}
-		pm_errno = PM_ERR_TRANS_COMMITING;
-		ret = -1;
-	}
-
 	_alpm_trans_free(trans);
 	handle->trans = NULL;
 
@@ -206,7 +218,7 @@ int SYMEXPORT alpm_trans_release()
 				alpm_option_get_lockfile());
 	}
 
-	return(ret);
+	return(0);
 }
 
 /** @} */
diff --git a/src/pacman/pacman.c b/src/pacman/pacman.c
index 2b748a1c..aa128261 100644
--- a/src/pacman/pacman.c
+++ b/src/pacman/pacman.c
@@ -207,9 +207,14 @@ static void cleanup(int signum)
 		pm_fprintf(stderr, PM_LOG_ERROR, "Internal pacman error: Segmentation fault.\n"
 		        "Please submit a full bug report with --debug if appropriate.\n");
 		exit(signum);
-	} else if((signum == SIGINT) && (alpm_trans_release() == -1)
-						&& (pm_errno == PM_ERR_TRANS_COMMITING)) {
-		return;
+	} else if((signum == SIGINT)) {
+		if(alpm_trans_interrupt() == 0) {
+			/* a transaction is being interrupted, don't exit pacman yet. */
+			return;
+		} else {
+			/* no commiting transaction, we can release it now and then exit pacman */
+			alpm_trans_release();
+		}
 	}
 
 	/* free alpm library resources */