CPU view: add mutexes

Signed-off-by: Jakub Skokan <jakub.skokan@havefun.cz>

diff --git a/bindings.c b/bindings.c
index fc335ee78d2792d33cda7ff00a7fcfa0181ea494..204e738048701b67b412ca8aed5c785c5f109267 100644 (file)
--- a/bindings.c
+++ b/bindings.c
@@ -293,12 +293,18 @@ struct cg_proc_stat {
        struct cpuacct_usage *usage; // Real usage as read from the host's /proc/stat
        struct cpuacct_usage *view; // Usage stats reported to the container
        int cpu_count;
+       pthread_mutex_t lock; // For node manipulation
        struct cg_proc_stat *next;
 };
 
 struct cg_proc_stat_head {
        struct cg_proc_stat *next;
        time_t lastcheck;
+
+       /*
+        * For access to the list. Reading can be parallel, pruning is exclusive.
+        */
+       pthread_rwlock_t lock;
 };
 
 #define CPUVIEW_HASH_SIZE 100
@@ -314,6 +320,13 @@ static bool cpuview_init_head(struct cg_proc_stat_head **head)
 
        (*head)->lastcheck = time(NULL);
        (*head)->next = NULL;
+
+       if (pthread_rwlock_init(&(*head)->lock, NULL) != 0) {
+               lxcfs_error("%s\n", "Failed to initialize list lock");
+               free(*head);
+               return false;
+       }
+
        return true;
 }
 
@@ -344,6 +357,7 @@ err:
 
 static void free_proc_stat_node(struct cg_proc_stat *node)
 {
+       pthread_mutex_destroy(&node->lock);
        free(node->cg);
        free(node->usage);
        free(node->view);
@@ -367,6 +381,7 @@ static void cpuview_free_head(struct cg_proc_stat_head *head)
                }
        }
 
+       pthread_rwlock_destroy(&head->lock);
        free(head);
 }
 
@@ -4189,25 +4204,32 @@ static void prune_proc_stat_history(void)
        time_t now = time(NULL);
 
        for (i = 0; i < CPUVIEW_HASH_SIZE; i++) {
-               if ((proc_stat_history[i]->lastcheck + PROC_STAT_PRUNE_INTERVAL) > now)
+               pthread_rwlock_wrlock(&proc_stat_history[i]->lock);
+
+               if ((proc_stat_history[i]->lastcheck + PROC_STAT_PRUNE_INTERVAL) > now) {
+                       pthread_rwlock_unlock(&proc_stat_history[i]->lock);
                        return;
+               }
 
-               if (!proc_stat_history[i]->next)
-                       continue;
+               if (proc_stat_history[i]->next) {
+                       proc_stat_history[i]->next = prune_proc_stat_list(proc_stat_history[i]->next);
+                       proc_stat_history[i]->lastcheck = now;
+               }
 
-               proc_stat_history[i]->next = prune_proc_stat_list(proc_stat_history[i]->next);
-               proc_stat_history[i]->lastcheck = now;
+               pthread_rwlock_unlock(&proc_stat_history[i]->lock);
        }
 }
 
-static struct cg_proc_stat *find_proc_stat_node(const char *cg)
+static struct cg_proc_stat *find_proc_stat_node(struct cg_proc_stat_head *head, const char *cg)
 {
-       int hash = calc_hash(cg) % CPUVIEW_HASH_SIZE;
-       struct cg_proc_stat_head *head = proc_stat_history[hash];
        struct cg_proc_stat *node;
 
-       if (!head->next)
+       pthread_rwlock_rdlock(&head->lock);
+
+       if (!head->next) {
+               pthread_rwlock_unlock(&head->lock);
                return NULL;
+       }
 
        node = head->next;
 
@@ -4219,6 +4241,7 @@ static struct cg_proc_stat *find_proc_stat_node(const char *cg)
        node = NULL;
 
 out:
+       pthread_rwlock_unlock(&head->lock);
        prune_proc_stat_history();
        return node;
 }
@@ -4255,6 +4278,11 @@ static struct cg_proc_stat *new_proc_stat_node(struct cpuacct_usage *usage, int
        node->cpu_count = cpu_count;
        node->next = NULL;
 
+       if (pthread_mutex_init(&node->lock, NULL) != 0) {
+               lxcfs_error("%s\n", "Failed to initialize node lock");
+               goto err;
+       }
+
        for (i = 0; i < cpu_count; i++) {
                node->view[i].user = 0;
                node->view[i].system = 0;
@@ -4276,19 +4304,28 @@ err:
        return NULL;
 }
 
-static void add_proc_stat_node(struct cg_proc_stat *new_node)
+static struct cg_proc_stat *add_proc_stat_node(struct cg_proc_stat *new_node)
 {
        int hash = calc_hash(new_node->cg) % CPUVIEW_HASH_SIZE;
        struct cg_proc_stat_head *head = proc_stat_history[hash];
-       struct cg_proc_stat *node;
+       struct cg_proc_stat *node, *rv = new_node;
+
+       pthread_rwlock_wrlock(&head->lock);
 
        if (!head->next) {
                head->next = new_node;
-               return;
+               goto out;
        }
 
+       node = head->next;
+
        for (;;) {
-               node = head->next;
+               if (strcmp(node->cg, new_node->cg) == 0) {
+                       /* The node is already present, return it */
+                       free_proc_stat_node(new_node);
+                       rv = node;
+                       goto out;
+               }
 
                if (node->next) {
                        node = node->next;
@@ -4296,8 +4333,33 @@ static void add_proc_stat_node(struct cg_proc_stat *new_node)
                }
 
                node->next = new_node;
-               return;
+               goto out;
+       }
+
+out:
+       pthread_rwlock_unlock(&head->lock);
+       return rv;
+}
+
+static struct cg_proc_stat *find_or_create_proc_stat_node(struct cpuacct_usage *usage, int cpu_count, const char *cg)
+{
+       int hash = calc_hash(cg) % CPUVIEW_HASH_SIZE;
+       struct cg_proc_stat_head *head = proc_stat_history[hash];
+       struct cg_proc_stat *node;
+
+       node = find_proc_stat_node(head, cg);
+
+       if (!node) {
+               node = new_proc_stat_node(usage, cpu_count, cg);
+               if (!node)
+                       return NULL;
+
+               node = add_proc_stat_node(node);
+               lxcfs_debug("New stat node (%d) for %s\n", cpu_count, cg);
        }
+
+       pthread_mutex_lock(&node->lock);
+       return node;
 }
 
 static void reset_proc_stat_node(struct cg_proc_stat *node, struct cpuacct_usage *usage, int cpu_count)
@@ -4383,16 +4445,12 @@ static int cpuview_proc_stat(const char *cg, const char *cpuset, struct cpuacct_
        if (max_cpus > cpu_cnt)
                max_cpus = cpu_cnt;
 
-       stat_node = find_proc_stat_node(cg);
+       stat_node = find_or_create_proc_stat_node(cg_cpu_usage, nprocs, cg);
 
        if (!stat_node) {
-               stat_node = new_proc_stat_node(cg_cpu_usage, nprocs, cg);
-               if (!stat_node) {
-                       rv = 0;
-                       goto err;
-               }
-
-               add_proc_stat_node(stat_node);
+               lxcfs_error("unable to find/create stat node for %s\n", cg);
+               rv = 0;
+               goto err;
        }
 
        diff = malloc(sizeof(struct cpuacct_usage) * nprocs);
@@ -4566,6 +4624,8 @@ static int cpuview_proc_stat(const char *cg, const char *cpuset, struct cpuacct_
        rv = total_len;
 
 err:
+       if (stat_node)
+               pthread_mutex_unlock(&stat_node->lock);
        if (line)
                free(line);
        if (diff)