[dpdk-dev] [PATCH v2 1/4] power: fix non thread-safe power env modification

[Hajkowski <marcinx.hajkowski@intel.com>]

From: Marcin Hajkowski <marcinx.hajkowski@intel.com>

Due to lack of thread safety in exisiting solution
use spinlock mechanism for atomic
modification of power environment related data.

Fixes: 445c6528b5 ("power: common interface for guest and host")
Cc: stable@dpdk.org

Signed-off-by: Marcin Hajkowski <marcinx.hajkowski@intel.com>
---
 doc/guides/rel_notes/release_19_05.rst |  2 ++
 lib/librte_power/rte_power.c           | 30 ++++++++++++++++++--------
 lib/librte_power/rte_power.h           |  2 +-
 3 files changed, 24 insertions(+), 10 deletions(-)

diff --git a/doc/guides/rel_notes/release_19_05.rst b/doc/guides/rel_notes/release_19_05.rst
index 61a2c7383..65371e4c8 100644
--- a/doc/guides/rel_notes/release_19_05.rst
+++ b/doc/guides/rel_notes/release_19_05.rst
@@ -120,6 +120,8 @@ API Changes
    Also, make sure to start the actual text at the margin.
    =========================================================
 
+   * power: ``rte_power_set_env`` and ``rte_power_unset_env`` functions
+     have been modified to be thread safe.
 
 ABI Changes
 -----------
diff --git a/lib/librte_power/rte_power.c b/lib/librte_power/rte_power.c
index a05fbef94..540d69be7 100644
--- a/lib/librte_power/rte_power.c
+++ b/lib/librte_power/rte_power.c
@@ -2,7 +2,7 @@
  * Copyright(c) 2010-2014 Intel Corporation
  */
 
-#include <rte_atomic.h>
+#include <rte_spinlock.h>
 
 #include "rte_power.h"
 #include "power_acpi_cpufreq.h"
@@ -12,7 +12,7 @@
 
 enum power_management_env global_default_env = PM_ENV_NOT_SET;
 
-volatile uint32_t global_env_cfg_status = 0;
+static rte_spinlock_t global_env_cfg_lock = RTE_SPINLOCK_INITIALIZER;
 
 /* function pointers */
 rte_power_freqs_t rte_power_freqs  = NULL;
@@ -30,9 +30,15 @@ rte_power_get_capabilities_t rte_power_get_capabilities;
 int
 rte_power_set_env(enum power_management_env env)
 {
-	if (rte_atomic32_cmpset(&global_env_cfg_status, 0, 1) == 0) {
+	rte_spinlock_lock(&global_env_cfg_lock);
+
+	if (global_default_env != PM_ENV_NOT_SET) {
+		rte_spinlock_unlock(&global_env_cfg_lock);
 		return 0;
 	}
+
+	int ret = 0;
+
 	if (env == PM_ENV_ACPI_CPUFREQ) {
 		rte_power_freqs = power_acpi_cpufreq_freqs;
 		rte_power_get_freq = power_acpi_cpufreq_get_freq;
@@ -73,18 +79,24 @@ rte_power_set_env(enum power_management_env env)
 	} else {
 		RTE_LOG(ERR, POWER, "Invalid Power Management Environment(%d) set\n",
 				env);
-		rte_power_unset_env();
-		return -1;
+		ret = -1;
 	}
-	global_default_env = env;
-	return 0;
+
+	if (ret == 0)
+		global_default_env = env;
+	else
+		global_default_env = PM_ENV_NOT_SET;
+
+	rte_spinlock_unlock(&global_env_cfg_lock);
+	return ret;
 }
 
 void
 rte_power_unset_env(void)
 {
-	if (rte_atomic32_cmpset(&global_env_cfg_status, 1, 0) != 0)
-		global_default_env = PM_ENV_NOT_SET;
+	rte_spinlock_lock(&global_env_cfg_lock);
+	global_default_env = PM_ENV_NOT_SET;
+	rte_spinlock_unlock(&global_env_cfg_lock);
 }
 
 enum power_management_env
diff --git a/lib/librte_power/rte_power.h b/lib/librte_power/rte_power.h
index c5e8f6b5b..54b76b4ee 100644
--- a/lib/librte_power/rte_power.h
+++ b/lib/librte_power/rte_power.h
@@ -26,7 +26,7 @@ enum power_management_env {PM_ENV_NOT_SET, PM_ENV_ACPI_CPUFREQ, PM_ENV_KVM_VM,
 /**
  * Set the default power management implementation. If this is not called prior
  * to rte_power_init(), then auto-detect of the environment will take place.
- * It is not thread safe.
+ * It is thread safe.
  *
  * @param env
  *  env. The environment in which to initialise Power Management for.
-- 
2.17.2