Add the sessiond notification-handling subsystem

[lttng-tools.git] / src / bin / lttng-sessiond / modprobe.c

diff --git a/src/bin/lttng-sessiond/modprobe.c b/src/bin/lttng-sessiond/modprobe.c
index 90fec711b8120c740d0ac4d48239b68c7db097c4..03545ef41d25b0acf21a5681431daf5d16e99794 100644 (file)
--- a/src/bin/lttng-sessiond/modprobe.c
+++ b/src/bin/lttng-sessiond/modprobe.c
@@ -16,6 +16,13 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
+/**
+ * @file modprobe.c
+ *
+ * @brief modprobe related functions.
+ *
+ */
+
 #define _LGPL_SOURCE
 #include <assert.h>
 #include <stdio.h>
@@ -50,6 +57,7 @@ struct kern_modules_param kern_modules_probes_default[] = {
        { "lttng-probe-ext3" },
        { "lttng-probe-ext4" },
        { "lttng-probe-gpio" },
+       { "lttng-probe-i2c" },
        { "lttng-probe-irq" },
        { "lttng-probe-jbd" },
        { "lttng-probe-jbd2" },
@@ -93,6 +101,9 @@ static int probes_capacity;
 #if HAVE_KMOD
 #include <libkmod.h>
 
+/**
+ * @brief Logging function for libkmod integration.
+ */
 static void log_kmod(void *data, int priority, const char *file, int line,
                const char *fn, const char *format, va_list args)
 {
@@ -106,6 +117,15 @@ static void log_kmod(void *data, int priority, const char *file, int line,
        free(str);
 }
 
+/**
+ * @brief Setup the libkmod context.
+ *
+ * Create the context, add a custom logging function and preload the
+ * ressources for faster operation.
+ *
+ * @returns    \c 0 on success
+ *             \c < 0 on error
+ */
 static int setup_kmod_ctx(struct kmod_ctx **ctx)
 {
        int ret = 0;
@@ -128,6 +148,19 @@ error:
        return ret;
 }
 
+/**
+ * @brief Loads the kernel modules in \p modules
+ *
+ * @param modules      List of modules to load
+ * @param entries      Number of modules in the list
+ * @param required     Are the modules required or optionnal
+ *
+ * If the modules are required, we will return with error after the
+ * first failed module load, otherwise we continue loading.
+ *
+ * @returns            \c 0 on success
+ *                     \c < 0 on error
+ */
 static int modprobe_lttng(struct kern_modules_param *modules,
                int entries, int required)
 {
@@ -148,9 +181,12 @@ static int modprobe_lttng(struct kern_modules_param *modules,
                        goto error;
                }
 
-               ret = kmod_module_probe_insert_module(mod, KMOD_PROBE_IGNORE_LOADED,
+               ret = kmod_module_probe_insert_module(mod, 0,
                                NULL, NULL, NULL, NULL);
-               if (ret < 0) {
+               if (ret == -EEXIST) {
+                       DBG("Module %s is already loaded", modules[i].name);
+                       ret = 0;
+               } else if (ret < 0) {
                        if (required) {
                                ERR("Unable to load required module %s",
                                                modules[i].name);
@@ -162,6 +198,7 @@ static int modprobe_lttng(struct kern_modules_param *modules,
                        }
                } else {
                        DBG("Modprobe successfully %s", modules[i].name);
+                       modules[i].loaded = true;
                }
 
                kmod_module_unref(mod);
@@ -174,6 +211,18 @@ error:
        return ret;
 }
 
+/**
+ * @brief Recursively unload modules.
+ *
+ * This function implements the same modules unloading behavior as
+ * 'modprobe -r' or rmmod, it will recursevily go trought the \p module
+ * dependencies and unload modules with a refcount of 0.
+ *
+ * @param mod          The module to unload
+ *
+ * @returns            \c 0 on success
+ *                     \c < 0 on error
+ */
 static int rmmod_recurse(struct kmod_module *mod) {
        int ret = 0;
        struct kmod_list *deps, *itr;
@@ -202,6 +251,14 @@ static int rmmod_recurse(struct kmod_module *mod) {
        return ret;
 }
 
+/**
+ * @brief Unloads the kernel modules in \p modules
+ *
+ * @param modules      List of modules to unload
+ * @param entries      Number of modules in the list
+ * @param required     Are the modules required or optionnal
+ *
+ */
 static void modprobe_remove_lttng(const struct kern_modules_param *modules,
                int entries, int required)
 {
@@ -216,6 +273,10 @@ static void modprobe_remove_lttng(const struct kern_modules_param *modules,
        for (i = entries - 1; i >= 0; i--) {
                struct kmod_module *mod = NULL;
 
+               if (!modules[i].loaded) {
+                       continue;
+               }
+
                ret = kmod_module_new_from_name(ctx, modules[i].name, &mod);
                if (ret < 0) {
                        PERROR("Failed to create kmod module for %s", modules[i].name);
@@ -282,6 +343,7 @@ static int modprobe_lttng(struct kern_modules_param *modules,
                        }
                } else {
                        DBG("Modprobe successfully %s", modules[i].name);
+                       modules[i].loaded = true;
                }
        }
 
@@ -296,6 +358,9 @@ static void modprobe_remove_lttng(const struct kern_modules_param *modules,
        char modprobe[256];
 
        for (i = entries - 1; i >= 0; i--) {
+               if (!modules[i].loaded) {
+                       continue;
+               }
                ret = snprintf(modprobe, sizeof(modprobe),
                                "/sbin/modprobe -r -q %s",
                                modules[i].name);