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Subject[PATCH 31/69] sysctl: remove .child from kernel/sched_domain/cpuX/domainY/
Date
Note: this patch makes sure to add empty kernel/sched_domain/cpuX/
directories when there are no domains in them.

This was the behaviour before this patch, and I thought it may need to
remain so in the new implementation. If they are not necessary this
can be removed to simplify the code.

Signed-off-by: Lucian Adrian Grijincu <lucian.grijincu@gmail.com>
---
kernel/sched.c | 266 ++++++++++++++++++++++++++++++++++++++------------------
1 files changed, 180 insertions(+), 86 deletions(-)
diff --git a/kernel/sched.c b/kernel/sched.c
index 23a980c..6e39b7c 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -6181,52 +6181,6 @@ static struct ctl_table sd_table_template[] = {
{ }
};

-static struct ctl_table sd_ctl_dir[] = {
- {
- .procname = "sched_domain",
- .mode = 0555,
- },
- {}
-};
-
-static struct ctl_table sd_ctl_root[] = {
- {
- .procname = "kernel",
- .mode = 0555,
- .child = sd_ctl_dir,
- },
- {}
-};
-
-static struct ctl_table *sd_alloc_ctl_entry(int n)
-{
- struct ctl_table *entry =
- kcalloc(n, sizeof(struct ctl_table), GFP_KERNEL);
-
- return entry;
-}
-
-static void sd_free_ctl_entry(struct ctl_table **tablep)
-{
- struct ctl_table *entry;
-
- /*
- * In the intermediate directories, both the child directory and
- * procname are dynamically allocated and could fail but the mode
- * will always be set. In the lowest directory the names are
- * static strings and all have proc handlers.
- */
- for (entry = *tablep; entry->mode; entry++) {
- if (entry->child)
- sd_free_ctl_entry(&entry->child);
- if (entry->proc_handler == NULL)
- kfree(entry->procname);
- }
-
- kfree(*tablep);
- *tablep = NULL;
-}
-
static struct ctl_table *
sd_alloc_ctl_domain_table(struct sched_domain *sd)
{
@@ -6250,64 +6204,204 @@ sd_alloc_ctl_domain_table(struct sched_domain *sd)
return table;
}

-static ctl_table *sd_alloc_ctl_cpu_table(int cpu)
+/*
+ * Find out what is the maximum number of domains in a cpu, and the
+ * total number of domains across all cpus.
+ */
+static void count_sd_domains(int *p_max, int *p_total)
{
- struct ctl_table *entry, *table;
- struct sched_domain *sd;
- int domain_num = 0, i;
- char buf[32];
+ int cpu;
+ int max = 0;
+ int total = 0;

- for_each_domain(cpu, sd)
- domain_num++;
- entry = table = sd_alloc_ctl_entry(domain_num + 1);
- if (table == NULL)
- return NULL;
+ for_each_possible_cpu(cpu) {
+ struct sched_domain *sd;
+ int domain_num = 0;

- i = 0;
- for_each_domain(cpu, sd) {
- snprintf(buf, 32, "domain%d", i);
- entry->procname = kstrdup(buf, GFP_KERNEL);
- entry->mode = 0555;
- entry->child = sd_alloc_ctl_domain_table(sd);
- entry++;
- i++;
+ for_each_domain(cpu, sd)
+ domain_num++;
+
+ if (domain_num > max)
+ max = domain_num;
+ total += domain_num;
}
- return table;
+ *p_max = max;
+ *p_total = total;
}

-static struct ctl_table_header *sd_sysctl_header;
+
+/* enough space to hold a string "cpu%d" or "domain%d" */
+#define SD_NAME_LEN 32
+typedef char sd_name_buf[SD_NAME_LEN];
+
+static sd_name_buf *sd_cpu_names, *sd_domain_names;
+static int sd_domain_headers_num, sd_cpudir_headers_num;
+static struct ctl_table_header **sd_domain_headers, **sd_cpudir_headers;
+
static void register_sched_domain_sysctl(void)
{
- int i, cpu_num = num_possible_cpus();
- struct ctl_table *entry = sd_alloc_ctl_entry(cpu_num + 1);
- char buf[32];
+ int cpu, i;
+ int cpu_num, max_domain_num;
+
+ /* possitions 2 and 3 in the array bellow */
+#define SD_PATH_CPU 2
+#define SD_PATH_DOM 3
+ struct ctl_path sd_path[] = {
+ { .procname = "kernel" },
+ { .procname = "sched_domain" },
+ { /* 'cpu0' */ },
+ { /* 'domain0' */ },
+ { },
+ };

- WARN_ON(sd_ctl_dir[0].child);
- sd_ctl_dir[0].child = entry;
+ sd_cpudir_headers_num = cpu_num = num_possible_cpus();
+ count_sd_domains(&max_domain_num, &sd_domain_headers_num);

- if (entry == NULL)
- return;
+ /*
+ * Allocate space for:
+ * - all cpu names (cpu0, cpu1,...) and all domain names (domain0,...)
+ * - the array of headers for cpu dirs kernel/sched_domain/cpuX/
+ * - the array of headers for domain dirs kernel/sched_domain/cpuX/domainY
+ *
+ * We only register the empty kernel/sched_domain/cpuX/ dirs
+ * to not break the ABI: if there were no domains defined, we
+ * would still have empty cpuX dir entries in
+ * kernel/sched_domain/.
+ *
+ * If this is not considered useful or part of the ABI, then
+ * we can drop the empty cpu dir entries.
+ */
+ sd_cpu_names = kmalloc(sizeof(sd_name_buf) * cpu_num, GFP_KERNEL);
+ if (sd_cpu_names == NULL)
+ goto fail_alloc_sd_cpu_names;

- for_each_possible_cpu(i) {
- snprintf(buf, 32, "cpu%d", i);
- entry->procname = kstrdup(buf, GFP_KERNEL);
- entry->mode = 0555;
- entry->child = sd_alloc_ctl_cpu_table(i);
- entry++;
+ sd_domain_names = kmalloc(sizeof(sd_name_buf) * max_domain_num, GFP_KERNEL);
+ if (sd_domain_names == NULL)
+ goto fail_alloc_sd_domain_names;
+
+ sd_cpudir_headers = kmalloc(sizeof(*sd_cpudir_headers) *
+ sd_cpudir_headers_num, GFP_KERNEL);
+ if (sd_cpudir_headers == NULL)
+ goto fail_alloc_sd_cpudir_headers;
+
+ sd_domain_headers = kmalloc(sizeof(*sd_domain_headers) *
+ sd_domain_headers_num, GFP_KERNEL);
+ if (sd_domain_headers == NULL)
+ goto fail_alloc_sd_domain_headers;
+
+ for_each_possible_cpu(cpu)
+ snprintf((char*)&sd_cpu_names[cpu], SD_NAME_LEN, "cpu%d", cpu);
+ for (i = 0; i < max_domain_num; i++)
+ snprintf((char*)&sd_domain_names[i], SD_NAME_LEN, "domain%d", i);
+
+ i = 0;
+ for_each_possible_cpu(cpu) {
+ struct ctl_table *empty = kzalloc(sizeof(*empty), GFP_KERNEL);
+ if (empty == NULL)
+ goto unregister_sd_cpudir_headers;
+ sd_path[SD_PATH_CPU].procname = sd_cpu_names[cpu];
+ sd_path[SD_PATH_DOM].procname = NULL; /* end of array sentinel */
+ sd_cpudir_headers[i] = register_sysctl_paths(sd_path, empty);
+ if (sd_cpudir_headers[i] == NULL) {
+ kfree(empty);
+ goto unregister_sd_cpudir_headers;
+ }
+ i++;
+ }
+
+ i = 0;
+ for_each_possible_cpu(cpu) {
+ struct sched_domain *sd;
+ int domain = 0;
+ for_each_domain(cpu, sd) {
+ struct ctl_table *table = sd_alloc_ctl_domain_table(sd);
+ if (table == NULL)
+ goto unregister_sd_domain_headers;
+ sd_path[SD_PATH_CPU].procname = sd_cpu_names[cpu];
+ sd_path[SD_PATH_DOM].procname = sd_domain_names[domain];
+ sd_domain_headers[i] = register_sysctl_paths(sd_path, table);
+ if (sd_domain_headers[i] == NULL) {
+ kfree(table);
+ goto unregister_sd_domain_headers;
+ }
+ i++;
+ domain++;
+ }
}

- WARN_ON(sd_sysctl_header);
- sd_sysctl_header = register_sysctl_table(sd_ctl_root);
+ return;
+
+unregister_sd_domain_headers:
+ i--; /* the current 'i' was being filled in, but fail_alloced */
+ for(; i >= 0; i--) {
+ struct ctl_table *table = sd_domain_headers[i]->ctl_table_arg;
+ unregister_sysctl_table(sd_domain_headers[i]);
+ kfree(table);
+ }
+ i = sd_cpudir_headers_num;
+unregister_sd_cpudir_headers:
+ i--;
+ for(; i >= 0; i--) {
+ struct ctl_table *table = sd_cpudir_headers[i]->ctl_table_arg;
+ unregister_sysctl_table(sd_cpudir_headers[i]);
+ kfree(table);
+ }
+
+ kfree(sd_domain_headers);
+fail_alloc_sd_domain_headers:
+ kfree(sd_cpudir_headers);
+fail_alloc_sd_cpudir_headers:
+ kfree(sd_domain_names);
+fail_alloc_sd_domain_names:
+ kfree(sd_cpu_names);
+fail_alloc_sd_cpu_names:
+ sd_domain_headers = NULL;
+ sd_cpudir_headers = NULL;
+ sd_domain_names = NULL;
+ sd_cpu_names = NULL;
+ sd_domain_headers_num = 0;
+ sd_cpudir_headers_num = 0;
}

/* may be called multiple times per register */
static void unregister_sched_domain_sysctl(void)
{
- if (sd_sysctl_header)
- unregister_sysctl_table(sd_sysctl_header);
- sd_sysctl_header = NULL;
- if (sd_ctl_dir[0].child)
- sd_free_ctl_entry(&sd_ctl_dir[0].child);
+ int i;
+
+ /* because this function may be called multiple times (not
+ * concurrently) for a single register_sched_domain_sysctl call,
+ * we skip unregistering if it was already done by a previous
+ * call. This is also why we make sure to NULLify all
+ * pointers: make sure nothing is double-freed. */
+ if (sd_domain_headers == NULL)
+ return;
+
+ /* unregister in the reverse order of registering, or we'll
+ * get a harmless warning saying that the parent of a header
+ * was registered before all it's children. */
+ for(i = sd_domain_headers_num - 1; i >= 0; i--) {
+ struct ctl_table *table = sd_domain_headers[i]->ctl_table_arg;
+ unregister_sysctl_table(sd_domain_headers[i]);
+ kfree(table);
+ }
+
+ for(i = sd_cpudir_headers_num - 1; i >= 0; i--) {
+ struct ctl_table *table = sd_cpudir_headers[i]->ctl_table_arg;
+ unregister_sysctl_table(sd_cpudir_headers[i]);
+ kfree(table);
+ }
+
+ kfree(sd_domain_headers);
+ kfree(sd_cpudir_headers);
+ kfree(sd_domain_names);
+ kfree(sd_cpu_names);
+
+ sd_domain_headers = NULL;
+ sd_cpudir_headers = NULL;
+ sd_domain_names = NULL;
+ sd_cpu_names = NULL;
+ sd_cpudir_headers_num = 0;
+ sd_domain_headers_num = 0;
}
#else
static void register_sched_domain_sysctl(void)
--
1.7.5.134.g1c08b


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