[dpdk-dev] [PATCH] lib/power: fix error handling on setting governor

[dpdk-dev] [PATCH] lib/power: fix error handling on setting governor

[David Hunt]

In the power_set_governor_*() functions, we using fputs() on /sys
filesystem. However, we also need to call fflush() to ensure that
the write completes successfully. Otherwise the attempt to set the
power governor fails and the function returns as if it has
succeeded. This patch adds an fflush to ensure that the
write succeeds, otherwise returns an error.

Fixes: e6c6dc0f96c8 ("power: add p-state driver compatibility")

Signed-off-by: David Hunt <david.hunt@intel.com>
---
 lib/librte_power/power_acpi_cpufreq.c   | 4 ++++
 lib/librte_power/power_pstate_cpufreq.c | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/lib/librte_power/power_acpi_cpufreq.c b/lib/librte_power/power_acpi_cpufreq.c
index 98dcde31d..45412f0b9 100644
--- a/lib/librte_power/power_acpi_cpufreq.c
+++ b/lib/librte_power/power_acpi_cpufreq.c
@@ -166,6 +166,10 @@ power_set_governor_userspace(struct rte_power_info *pi)
 	val = fputs(POWER_GOVERNOR_USERSPACE, f);
 	FOPS_OR_ERR_GOTO(val, out);
 
+	/* We need to flush to see if the fputs succeeds */
+	val = fflush(f);
+	FOPS_OR_ERR_GOTO(val, out);
+
 	ret = 0;
 	RTE_LOG(INFO, POWER, "Power management governor of lcore %u has been "
 			"set to user space successfully\n", pi->lcore_id);
diff --git a/lib/librte_power/power_pstate_cpufreq.c b/lib/librte_power/power_pstate_cpufreq.c
index 9ec5da511..c4d972fc0 100644
--- a/lib/librte_power/power_pstate_cpufreq.c
+++ b/lib/librte_power/power_pstate_cpufreq.c
@@ -308,6 +308,10 @@ power_set_governor_performance(struct pstate_power_info *pi)
 	val = fputs(POWER_GOVERNOR_PERF, f);
 	FOPS_OR_ERR_GOTO(val, out);
 
+	/* We need to flush to see if the fputs succeeds */
+	val = fflush(f);
+	FOPS_OR_ERR_GOTO(val, out);
+
 	ret = 0;
 	RTE_LOG(INFO, POWER, "Power management governor of lcore %u has been "
 			"set to performance successfully\n", pi->lcore_id);
-- 
2.17.1

Re: [dpdk-dev] [PATCH] lib/power: fix error handling on setting governor

[Thomas Monjalon]

08/01/2019 15:59, David Hunt:
> In the power_set_governor_*() functions, we using fputs() on /sys
> filesystem. However, we also need to call fflush() to ensure that
> the write completes successfully. Otherwise the attempt to set the
> power governor fails and the function returns as if it has
> succeeded. This patch adds an fflush to ensure that the
> write succeeds, otherwise returns an error.
> 
> Fixes: e6c6dc0f96c8 ("power: add p-state driver compatibility")
> 
> Signed-off-by: David Hunt <david.hunt@intel.com>

Applied, thanks