doc: add Meson coding style to contributors guide

[dpdk.git] / lib / librte_power / power_acpi_cpufreq.c

diff --git a/lib/librte_power/power_acpi_cpufreq.c b/lib/librte_power/power_acpi_cpufreq.c
index 583815a..84a9d75 100644 (file)
--- a/lib/librte_power/power_acpi_cpufreq.c
+++ b/lib/librte_power/power_acpi_cpufreq.c
@@ -12,7 +12,6 @@
 #include <signal.h>
 #include <limits.h>
 
-#include <rte_atomic.h>
 #include <rte_memcpy.h>
 #include <rte_memory.h>
 #include <rte_string_fns.h>
@@ -86,7 +85,7 @@ struct rte_power_info {
        FILE *f;                             /**< FD of scaling_setspeed */
        char governor_ori[32];               /**< Original governor name */
        uint32_t curr_idx;                   /**< Freq index in freqs array */
-       volatile uint32_t state;             /**< Power in use state */
+       uint32_t state;                      /**< Power in use state */
        uint16_t turbo_available;            /**< Turbo Boost available */
        uint16_t turbo_enable;               /**< Turbo Boost enable/disable */
 } __rte_cache_aligned;
@@ -300,6 +299,7 @@ int
 power_acpi_cpufreq_init(unsigned int lcore_id)
 {
        struct rte_power_info *pi;
+       uint32_t exp_state;
 
        if (lcore_id >= RTE_MAX_LCORE) {
                RTE_LOG(ERR, POWER, "Lcore id %u can not exceeds %u\n",
@@ -308,8 +308,16 @@ power_acpi_cpufreq_init(unsigned int lcore_id)
        }
 
        pi = &lcore_power_info[lcore_id];
-       if (rte_atomic32_cmpset(&(pi->state), POWER_IDLE, POWER_ONGOING)
-                       == 0) {
+       exp_state = POWER_IDLE;
+       /* The power in use state works as a guard variable between
+        * the CPU frequency control initialization and exit process.
+        * The ACQUIRE memory ordering here pairs with the RELEASE
+        * ordering below as lock to make sure the frequency operations
+        * in the critical section are done under the correct state.
+        */
+       if (!__atomic_compare_exchange_n(&(pi->state), &exp_state,
+                                       POWER_ONGOING, 0,
+                                       __ATOMIC_ACQUIRE, __ATOMIC_RELAXED)) {
                RTE_LOG(INFO, POWER, "Power management of lcore %u is "
                                "in use\n", lcore_id);
                return -1;
@@ -346,12 +354,16 @@ power_acpi_cpufreq_init(unsigned int lcore_id)
 
        RTE_LOG(INFO, POWER, "Initialized successfully for lcore %u "
                        "power management\n", lcore_id);
-       rte_atomic32_cmpset(&(pi->state), POWER_ONGOING, POWER_USED);
+       exp_state = POWER_ONGOING;
+       __atomic_compare_exchange_n(&(pi->state), &exp_state, POWER_USED,
+                                   0, __ATOMIC_RELEASE, __ATOMIC_RELAXED);
 
        return 0;
 
 fail:
-       rte_atomic32_cmpset(&(pi->state), POWER_ONGOING, POWER_UNKNOWN);
+       exp_state = POWER_ONGOING;
+       __atomic_compare_exchange_n(&(pi->state), &exp_state, POWER_UNKNOWN,
+                                   0, __ATOMIC_RELEASE, __ATOMIC_RELAXED);
 
        return -1;
 }
@@ -408,6 +420,7 @@ int
 power_acpi_cpufreq_exit(unsigned int lcore_id)
 {
        struct rte_power_info *pi;
+       uint32_t exp_state;
 
        if (lcore_id >= RTE_MAX_LCORE) {
                RTE_LOG(ERR, POWER, "Lcore id %u can not exceeds %u\n",
@@ -415,8 +428,16 @@ power_acpi_cpufreq_exit(unsigned int lcore_id)
                return -1;
        }
        pi = &lcore_power_info[lcore_id];
-       if (rte_atomic32_cmpset(&(pi->state), POWER_USED, POWER_ONGOING)
-                       == 0) {
+       exp_state = POWER_USED;
+       /* The power in use state works as a guard variable between
+        * the CPU frequency control initialization and exit process.
+        * The ACQUIRE memory ordering here pairs with the RELEASE
+        * ordering below as lock to make sure the frequency operations
+        * in the critical section are done under the correct state.
+        */
+       if (!__atomic_compare_exchange_n(&(pi->state), &exp_state,
+                                       POWER_ONGOING, 0,
+                                       __ATOMIC_ACQUIRE, __ATOMIC_RELAXED)) {
                RTE_LOG(INFO, POWER, "Power management of lcore %u is "
                                "not used\n", lcore_id);
                return -1;
@@ -436,12 +457,16 @@ power_acpi_cpufreq_exit(unsigned int lcore_id)
        RTE_LOG(INFO, POWER, "Power management of lcore %u has exited from "
                        "'userspace' mode and been set back to the "
                        "original\n", lcore_id);
-       rte_atomic32_cmpset(&(pi->state), POWER_ONGOING, POWER_IDLE);
+       exp_state = POWER_ONGOING;
+       __atomic_compare_exchange_n(&(pi->state), &exp_state, POWER_IDLE,
+                                   0, __ATOMIC_RELEASE, __ATOMIC_RELAXED);
 
        return 0;
 
 fail:
-       rte_atomic32_cmpset(&(pi->state), POWER_ONGOING, POWER_UNKNOWN);
+       exp_state = POWER_ONGOING;
+       __atomic_compare_exchange_n(&(pi->state), &exp_state, POWER_UNKNOWN,
+                                   0, __ATOMIC_RELEASE, __ATOMIC_RELAXED);
 
        return -1;
 }