[PATCH 1/1] rasdaemon: Fix for regression in ras_mc_create_table() if some cpus are offline at the system start

[<shiju.jose@huawei.com>]

From: Shiju Jose <shiju.jose@huawei.com>

Issues:
Regression in the ras_mc_create_table() if some of the cpus are offline
at the system start when run the rasdaemon. This issue is
reproducible in ras_mc_create_table() with decode and record
non-standard events and reproducible sometimes with
ras_mc_create_table() for the standard events.
Also in the multi thread way, there is memory leak in ras_mc_event_opendb()
as struct sqlite3_priv *priv and sqlite3 *db allocated/initialized per
thread, but stored in the common struct ras_events ras in pthread data,
which is shared across the threads. 

Reason:
when the system start with some of the cpus are offline and then run
the rasdaemon, read_ras_event_all_cpus() exit with error and switch to
the multi thread way. However read() in read_ras_event() return error in
threads for each of the offline CPUs and does clean up including calling
ras_mc_event_closedb().
Since the 'struct ras_events ras' passed in the pthread_data to each of the
threads is common, struct sqlite3_priv *priv and sqlite3 *db allocated/
initialized per thread and stored in the common 'struct ras_events ras',
are getting overwritten in each ras_mc_event_opendb()(which called from
pthread per cpu), result memory leak. Also when ras_mc_event_closedb()
is called in the above error case from the threads corresponding to the
offline cpus, close the sqlite3 *db and free sqlite3_priv *priv stored
in the common 'struct ras_events ras', result regression when accessing
priv->db in the ras_mc_create_table() from another context later.

Proposed solution:
In ras_mc_event_opendb(), allocate struct sqlite3_priv *priv,
init sqlite3 *db and create tables common for the threads with shared
'struct ras_events ras' based on a reference count and free them in the
same way.
Also protect critical code ras_mc_event_opendb() and ras_mc_event_closedb()
using mutex in the multi thread case from any regression caused by the
thread pre-emption.

Reported-by: Lei Feng <fenglei47@h-partners.com>
Signed-off-by: Shiju Jose <shiju.jose@huawei.com>
---
 ras-events.c | 16 +++++++++++++++-
 ras-events.h |  4 +++-
 ras-record.c |  9 +++++++++
 3 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/ras-events.c b/ras-events.c
index 49e4f9a..4d21af3 100644
--- a/ras-events.c
+++ b/ras-events.c
@@ -625,19 +625,25 @@ static void *handle_ras_events_cpu(void *priv)
 
 	log(TERM, LOG_INFO, "Listening to events on cpu %d\n", pdata->cpu);
 	if (pdata->ras->record_events) {
+		pthread_mutex_lock(&pdata->ras->db_lock);
 		if (ras_mc_event_opendb(pdata->cpu, pdata->ras)) {
+			pthread_mutex_unlock(&pdata->ras->db_lock);
 			log(TERM, LOG_ERR, "Can't open database\n");
 			close(fd);
 			kbuffer_free(kbuf);
 			free(page);
 			return 0;
 		}
+		pthread_mutex_unlock(&pdata->ras->db_lock);
 	}
 
 	read_ras_event(fd, pdata, kbuf, page);
 
-	if (pdata->ras->record_events)
+	if (pdata->ras->record_events) {
+		pthread_mutex_lock(&pdata->ras->db_lock);
 		ras_mc_event_closedb(pdata->cpu, pdata->ras);
+		pthread_mutex_unlock(&pdata->ras->db_lock);
+	}
 
 	close(fd);
 	kbuffer_free(kbuf);
@@ -993,6 +999,11 @@ int handle_ras_events(int record_events)
 
 	/* Poll doesn't work on this kernel. Fallback to pthread way */
 	if (rc == -255) {
+		if (pthread_mutex_init(&ras->db_lock, NULL) != 0) {
+			log(SYSLOG, LOG_INFO, "sqlite db lock init has failed\n");
+			goto err;
+		}
+
 		log(SYSLOG, LOG_INFO,
 		"Opening one thread per cpu (%d threads)\n", cpus);
 		for (i = 0; i < cpus; i++) {
@@ -1005,6 +1016,8 @@ int handle_ras_events(int record_events)
 				i);
 				while (--i)
 					pthread_cancel(data[i].thread);
+
+				pthread_mutex_destroy(&ras->db_lock);
 				goto err;
 			}
 		}
@@ -1012,6 +1025,7 @@ int handle_ras_events(int record_events)
 		/* Wait for all threads to complete */
 		for (i = 0; i < cpus; i++)
 			pthread_join(data[i].thread, NULL);
+		pthread_mutex_destroy(&ras->db_lock);
 	}
 
 	log(SYSLOG, LOG_INFO, "Huh! something got wrong. Aborting.\n");
diff --git a/ras-events.h b/ras-events.h
index 6c9f507..649b0c0 100644
--- a/ras-events.h
+++ b/ras-events.h
@@ -56,7 +56,9 @@ struct ras_events {
 	time_t		uptime_diff;
 
 	/* For ras-record */
-	void		*db_priv;
+	void	*db_priv;
+	int	db_ref_count;
+	pthread_mutex_t db_lock;
 
 	/* For the mce handler */
 	struct mce_priv	*mce_priv;
diff --git a/ras-record.c b/ras-record.c
index a367939..171704a 100644
--- a/ras-record.c
+++ b/ras-record.c
@@ -763,6 +763,10 @@ int ras_mc_event_opendb(unsigned cpu, struct ras_events *ras)
 
 	printf("Calling %s()\n", __FUNCTION__);
 
+	ras->db_ref_count++;
+	if (ras->db_ref_count > 1)
+		return 0;
+
 	ras->db_priv = NULL;
 
 	priv = calloc(1, sizeof(*priv));
@@ -912,6 +916,13 @@ int ras_mc_event_closedb(unsigned int cpu, struct ras_events *ras)
 
 	printf("Calling %s()\n", __func__);
 
+	if (ras->db_ref_count > 0)
+		ras->db_ref_count--;
+	else
+		return -1;
+	if (ras->db_ref_count > 0)
+		return 0;
+
 	if (!priv)
 		return -1;
 
@@ -1018,6 +1026,7 @@ int ras_mc_event_closedb(unsigned int cpu, struct ras_events *ras)
 		log(TERM, LOG_ERR,
 		    "cpu %u: Failed to shutdown sqlite: error = %d\n", cpu, rc);
 	free(priv);
+	ras->db_priv = NULL;
 
 	return 0;
 }
-- 
2.25.1