Clarify terminolgy around cpu ids and array length

Rename 'num_possible_cpus' to 'possible_cpus_array_len' to make it
clearer that we use this value to create arrays of per-CPU elements.

Change-Id: Ie5dc9293a95bf321f8add7e9c44ac677bc1fe539
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/src/common/counter/counter.c b/src/common/counter/counter.c
index b71b43ae7c3828b2c317d4fd10d8036e827aa7bc..60edad0c5b63b9ea2a1f3f92e9ca42e5ab400217 100644 (file)
--- a/src/common/counter/counter.c
+++ b/src/common/counter/counter.c
@@ -118,7 +118,7 @@ int lttng_counter_set_cpu_shm(struct lib_counter *counter, int cpu, int fd)
        struct lib_counter_config *config = &counter->config;
        struct lib_counter_layout *layout;
 
-       if (cpu < 0 || cpu >= num_possible_cpus())
+       if (cpu < 0 || cpu >= get_possible_cpus_array_len())
                return -EINVAL;
 
        if (!(config->alloc & COUNTER_ALLOC_PER_CPU))
@@ -171,7 +171,7 @@ int validate_args(const struct lib_counter_config *config,
        int nr_counter_cpu_fds,
        const int *counter_cpu_fds)
 {
-       int nr_cpus = num_possible_cpus();
+       int nr_cpus = get_possible_cpus_array_len();
 
        if (CAA_BITS_PER_LONG != 64 && config->counter_size == COUNTER_SIZE_64_BIT) {
                WARN_ON_ONCE(1);
@@ -210,7 +210,7 @@ struct lib_counter *lttng_counter_create(const struct lib_counter_config *config
        size_t dimension, nr_elem = 1;
        int cpu, ret;
        int nr_handles = 0;
-       int nr_cpus = num_possible_cpus();
+       int nr_cpus = get_possible_cpus_array_len();
 
        if (validate_args(config, nr_dimensions, max_nr_elem,
                        global_sum_step, global_counter_fd, nr_counter_cpu_fds,
@@ -309,7 +309,7 @@ int lttng_counter_get_cpu_shm(struct lib_counter *counter, int cpu, int *fd, siz
        struct lib_counter_layout *layout;
        int shm_fd;
 
-       if (cpu >= num_possible_cpus())
+       if (cpu >= get_possible_cpus_array_len())
                return -1;
        layout = &counter->percpu_counters[cpu];
        shm_fd = layout->shm_fd;
@@ -335,13 +335,13 @@ int lttng_counter_read(const struct lib_counter_config *config,
 
        switch (config->alloc) {
        case COUNTER_ALLOC_PER_CPU:
-               if (cpu < 0 || cpu >= num_possible_cpus())
+               if (cpu < 0 || cpu >= get_possible_cpus_array_len())
                        return -EINVAL;
                layout = &counter->percpu_counters[cpu];
                break;
        case COUNTER_ALLOC_PER_CPU | COUNTER_ALLOC_GLOBAL:
                if (cpu >= 0) {
-                       if (cpu >= num_possible_cpus())
+                       if (cpu >= get_possible_cpus_array_len())
                                return -EINVAL;
                        layout = &counter->percpu_counters[cpu];
                } else {
@@ -469,13 +469,13 @@ int lttng_counter_clear_cpu(const struct lib_counter_config *config,
 
        switch (config->alloc) {
        case COUNTER_ALLOC_PER_CPU:
-               if (cpu < 0 || cpu >= num_possible_cpus())
+               if (cpu < 0 || cpu >= get_possible_cpus_array_len())
                        return -EINVAL;
                layout = &counter->percpu_counters[cpu];
                break;
        case COUNTER_ALLOC_PER_CPU | COUNTER_ALLOC_GLOBAL:
                if (cpu >= 0) {
-                       if (cpu >= num_possible_cpus())
+                       if (cpu >= get_possible_cpus_array_len())
                                return -EINVAL;
                        layout = &counter->percpu_counters[cpu];
                } else {

diff --git a/src/common/ringbuffer/ring_buffer_frontend.c b/src/common/ringbuffer/ring_buffer_frontend.c
index 91c69b7697d9e7f1bd1b06a518a66049a8ce210c..817cc842a3d49373773b714c184cbc4058395a65 100644 (file)
--- a/src/common/ringbuffer/ring_buffer_frontend.c
+++ b/src/common/ringbuffer/ring_buffer_frontend.c
@@ -982,7 +982,7 @@ struct lttng_ust_shm_handle *channel_create(const struct lttng_ust_ring_buffer_c
        int64_t blocking_timeout_ms;
 
        if (config->alloc == RING_BUFFER_ALLOC_PER_CPU)
-               nr_streams = num_possible_cpus();
+               nr_streams = get_possible_cpus_array_len();
        else
                nr_streams = 1;
 
@@ -1011,7 +1011,7 @@ struct lttng_ust_shm_handle *channel_create(const struct lttng_ust_ring_buffer_c
                return NULL;
 
        /* Allocate table for channel + per-cpu buffers */
-       handle->table = shm_object_table_create(1 + num_possible_cpus());
+       handle->table = shm_object_table_create(1 + get_possible_cpus_array_len());
        if (!handle->table)
                goto error_table_alloc;
 
@@ -1095,7 +1095,7 @@ struct lttng_ust_shm_handle *channel_handle_create(void *data,
                return NULL;
 
        /* Allocate table for channel + per-cpu buffers */
-       handle->table = shm_object_table_create(1 + num_possible_cpus());
+       handle->table = shm_object_table_create(1 + get_possible_cpus_array_len());
        if (!handle->table)
                goto error_table_alloc;
        /* Add channel object */
@@ -1190,7 +1190,7 @@ struct lttng_ust_ring_buffer *channel_get_ring_buffer(
        if (config->alloc == RING_BUFFER_ALLOC_GLOBAL) {
                cpu = 0;
        } else {
-               if (cpu >= num_possible_cpus())
+               if (cpu >= get_possible_cpus_array_len())
                        return NULL;
        }
        ref = &chan->backend.buf[cpu].shmp._ref;
@@ -1235,7 +1235,7 @@ int ring_buffer_stream_close_wait_fd(const struct lttng_ust_ring_buffer_config *
        if (config->alloc == RING_BUFFER_ALLOC_GLOBAL) {
                cpu = 0;
        } else {
-               if (cpu >= num_possible_cpus())
+               if (cpu >= get_possible_cpus_array_len())
                        return -EINVAL;
        }
        ref = &chan->backend.buf[cpu].shmp._ref;
@@ -1253,7 +1253,7 @@ int ring_buffer_stream_close_wakeup_fd(const struct lttng_ust_ring_buffer_config
        if (config->alloc == RING_BUFFER_ALLOC_GLOBAL) {
                cpu = 0;
        } else {
-               if (cpu >= num_possible_cpus())
+               if (cpu >= get_possible_cpus_array_len())
                        return -EINVAL;
        }
        ref = &chan->backend.buf[cpu].shmp._ref;

diff --git a/src/common/smp.c b/src/common/smp.c
index 5bcbad8113d82b8971574912d09320db3d2631c3..8bbf9f6f1f0441ab94e4f9c271fa3e5097231d3e 100644 (file)
--- a/src/common/smp.c
+++ b/src/common/smp.c
@@ -25,7 +25,7 @@
 
 #define __max(a,b) ((a)>(b)?(a):(b))
 
-static int num_possible_cpus_cache;
+static int possible_cpus_array_len_cache;
 
 /*
  * As a fallback to parsing the CPU mask in "/sys/devices/system/cpu/possible",
@@ -146,14 +146,14 @@ end:
 }
 
 /*
- * Get the number of CPUs from the possible cpu mask.
+ * Get the highest CPU id from a CPU mask.
  *
  * pmask: the mask to parse.
  * len: the len of the mask excluding '\0'.
  *
- * Returns the number of possible CPUs from the mask or 0 on error.
+ * Returns the highest CPU id from the mask or -1 on error.
  */
-int get_num_possible_cpus_from_mask(const char *pmask, size_t len)
+int get_max_cpuid_from_mask(const char *pmask, size_t len)
 {
        ssize_t i;
        unsigned long cpu_index;
@@ -179,13 +179,13 @@ int get_num_possible_cpus_from_mask(const char *pmask, size_t len)
         * CPUs.
         */
        if ((&pmask[i] != endptr) && (cpu_index < INT_MAX))
-               return (int) cpu_index + 1;
+               return (int) cpu_index;
 
 error:
-       return 0;
+       return -1;
 }
 
-static void _get_num_possible_cpus(void)
+static void update_possible_cpus_array_len_cache(void)
 {
        int ret;
        char buf[LTTNG_UST_CPUMASK_SIZE];
@@ -196,9 +196,12 @@ static void _get_num_possible_cpus(void)
                goto fallback;
 
        /* Parse the possible cpu mask, on failure fallback to sysconf. */
-       ret = get_num_possible_cpus_from_mask((char *) &buf, ret);
-       if (ret > 0)
+       ret = get_max_cpuid_from_mask((char *) &buf, ret);
+       if (ret >= 0) {
+               /* Add 1 to convert from max cpuid to an array len. */
+               ret++;
                goto end;
+       }
 
 fallback:
        /* Fallback to sysconf. */
@@ -209,20 +212,24 @@ end:
        if (ret < 1)
                return;
 
-       num_possible_cpus_cache = ret;
+       possible_cpus_array_len_cache = ret;
 }
 
 /*
- * Returns the total number of CPUs in the system. If the cache is not yet
- * initialized, get the value from "/sys/devices/system/cpu/possible" or
- * fallback to sysconf and cache it.
+ * Returns the length of an array that could contain a per-CPU element for each
+ * possible CPU id for the lifetime of the process.
+ *
+ * We currently assume CPU ids are contiguous up the maximum CPU id.
+ *
+ * If the cache is not yet initialized, get the value from
+ * "/sys/devices/system/cpu/possible" or fallback to sysconf and cache it.
  *
  * If all methods fail, don't populate the cache and return 0.
  */
-int num_possible_cpus(void)
+int get_possible_cpus_array_len(void)
 {
-       if (caa_unlikely(!num_possible_cpus_cache))
-               _get_num_possible_cpus();
+       if (caa_unlikely(!possible_cpus_array_len_cache))
+               update_possible_cpus_array_len_cache();
 
-       return num_possible_cpus_cache;
+       return possible_cpus_array_len_cache;
 }

diff --git a/src/common/smp.h b/src/common/smp.h
index 51fbd2d7e5d34c01c04df7d13ac4397302a223c0..f908b6c6ef39c5e9f8868ec15b19a78f80b54d83 100644 (file)
--- a/src/common/smp.h
+++ b/src/common/smp.h
@@ -30,27 +30,31 @@ int get_num_possible_cpus_fallback(void)
        __attribute__((visibility("hidden")));
 
 /*
- * Get the number of CPUs from the possible cpu mask.
+ * Get the highest CPU id from a CPU mask.
  *
  * pmask: the mask to parse.
  * len: the len of the mask excluding '\0'.
  *
- * Returns the number of possible CPUs from the mask or 0 on error.
+ * Returns the highest CPU id from the mask or -1 on error.
  */
-int get_num_possible_cpus_from_mask(const char *pmask, size_t len)
+int get_max_cpuid_from_mask(const char *pmask, size_t len)
        __attribute__((visibility("hidden")));
 
 /*
- * Returns the total number of CPUs in the system. If the cache is not yet
- * initialized, get the value from "/sys/devices/system/cpu/possible" or
- * fallback to sysconf and cache it.
+ * Returns the length of an array that could contain a per-CPU element for each
+ * possible CPU id for the lifetime of the process.
+ *
+ * We currently assume CPU ids are contiguous up the maximum CPU id.
+ *
+ * If the cache is not yet initialized, get the value from
+ * "/sys/devices/system/cpu/possible" or fallback to sysconf and cache it.
  *
  * If all methods fail, don't populate the cache and return 0.
  */
-int num_possible_cpus(void)
+int get_possible_cpus_array_len(void)
        __attribute__((visibility("hidden")));
 
 #define for_each_possible_cpu(cpu)             \
-       for ((cpu) = 0; (cpu) < num_possible_cpus(); (cpu)++)
+       for ((cpu) = 0; (cpu) < get_possible_cpus_array_len(); (cpu)++)
 
 #endif /* _UST_COMMON_SMP_H */

diff --git a/src/lib/lttng-ust-ctl/ustctl.c b/src/lib/lttng-ust-ctl/ustctl.c
index bcbd9c66c2a2b01da949e7f85a6a3628a34c49dc..6faaef5ed44ff4fcc88a31b181ddd511c3f87cce 100644 (file)
--- a/src/lib/lttng-ust-ctl/ustctl.c
+++ b/src/lib/lttng-ust-ctl/ustctl.c
@@ -1384,7 +1384,7 @@ error:
 
 int lttng_ust_ctl_get_nr_stream_per_channel(void)
 {
-       return num_possible_cpus();
+       return get_possible_cpus_array_len();
 }
 
 struct lttng_ust_ctl_consumer_channel *
@@ -2904,7 +2904,7 @@ int lttng_ust_ctl_regenerate_statedump(int sock, int handle)
 
 int lttng_ust_ctl_get_nr_cpu_per_counter(void)
 {
-       return num_possible_cpus();
+       return get_possible_cpus_array_len();
 }
 
 struct lttng_ust_ctl_daemon_counter *

diff --git a/tests/unit/libcommon/test_smp.c b/tests/unit/libcommon/test_smp.c
index 8f9a4042ba1aab0b76eb01d5721e3dee3c06b32f..7180076b7fd5db386746055b5ec932ce5a7ed00f 100644 (file)
--- a/tests/unit/libcommon/test_smp.c
+++ b/tests/unit/libcommon/test_smp.c
@@ -21,43 +21,43 @@ struct parse_test_data {
 };
 
 static struct parse_test_data parse_test_data[] = {
-       { "", 0 },
-       { "abc", 0 },
-       { ",,,", 0 },
-       { "--", 0 },
-       { ",", 0 },
-       { "-", 0 },
-       { "2147483647", 0 },
-       { "18446744073709551615", 0 },
-       { "0-2147483647", 0 },
-       { "0-18446744073709551615", 0 },
-       { "0", 1 },
-       { "1", 2 },
-       { "0-1", 2 },
-       { "1-3", 4 },
-       { "0,2", 3 },
-       { "1,2", 3 },
-       { "0,4-6,127", 128 },
-       { "0-4095", 4096 },
+       { "", -1 },
+       { "abc", -1 },
+       { ",,,", -1 },
+       { "--", -1 },
+       { ",", -1 },
+       { "-", -1 },
+       { "2147483647", -1 },
+       { "18446744073709551615", -1 },
+       { "0-2147483647", -1 },
+       { "0-18446744073709551615", -1 },
+       { "0", 0 },
+       { "1", 1 },
+       { "0-1", 1 },
+       { "1-3", 3 },
+       { "0,2", 2 },
+       { "1,2", 2 },
+       { "0,4-6,127", 127 },
+       { "0-4095", 4095 },
 
-       { "\n", 0 },
-       { "abc\n", 0 },
-       { ",,,\n", 0 },
-       { "--\n", 0 },
-       { ",\n", 0 },
-       { "-\n", 0 },
-       { "2147483647\n", 0 },
-       { "18446744073709551615\n", 0 },
-       { "0-2147483647\n", 0 },
-       { "0-18446744073709551615\n", 0 },
-       { "0\n", 1 },
-       { "1\n", 2 },
-       { "0-1\n", 2 },
-       { "1-3\n", 4 },
-       { "0,2\n", 3 },
-       { "1,2\n", 3 },
-       { "0,4-6,127\n", 128 },
-       { "0-4095\n", 4096 },
+       { "\n", -1 },
+       { "abc\n", -1 },
+       { ",,,\n", -1 },
+       { "--\n", -1 },
+       { ",\n", -1 },
+       { "-\n", -1 },
+       { "2147483647\n", -1 },
+       { "18446744073709551615\n", -1 },
+       { "0-2147483647\n", -1 },
+       { "0-18446744073709551615\n", -1 },
+       { "0\n", 0 },
+       { "1\n", 1 },
+       { "0-1\n", 1 },
+       { "1-3\n", 3 },
+       { "0,2\n", 2 },
+       { "1,2\n", 2 },
+       { "0,4-6,127\n", 127 },
+       { "0-4095\n", 4095 },
 };
 
 static int parse_test_data_len = sizeof(parse_test_data) / sizeof(parse_test_data[0]);
@@ -71,14 +71,14 @@ int main(void)
        diag("Testing smp helpers");
 
        for (i = 0; i < parse_test_data_len; i++) {
-               ret = get_num_possible_cpus_from_mask(parse_test_data[i].buf,
+               ret = get_max_cpuid_from_mask(parse_test_data[i].buf,
                                strlen(parse_test_data[i].buf));
                ok(ret == parse_test_data[i].expected,
-                       "get_num_possible_cpus_from_mask '%s', expected: '%d', result: '%d'",
+                       "get_max_cpuid_from_mask '%s', expected: '%d', result: '%d'",
                        parse_test_data[i].buf, parse_test_data[i].expected, ret);
        }
 
-       ok(num_possible_cpus() > 0, "num_possible_cpus (%d > 0)", num_possible_cpus());
+       ok(get_possible_cpus_array_len() > 0, "get_possible_cpus_array_len (%d > 0)", get_possible_cpus_array_len());
 
        return exit_status();
 }