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tools/power turbostat: Fix /dev/cpu_dma_latency warnings

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[ Upstream commit 40aafc7d58d3544f152a863a0e9863014b6d5d8c ]

When running as non-root the following error is seen in turbostat:

turbostat: fopen /dev/cpu_dma_latency
: Permission denied

turbostat and the man page have information on how to avoid other
permission errors, so these can be fixed the same way.

Provide better /dev/cpu_dma_latency warnings that provide instructions on
how to avoid the error, and update the man page.

Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Cc: linux-pm@vger.kernel.org
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Prarit Bhargava 2022-12-15 10:18:16 -05:00 committed by Greg Kroah-Hartman
parent 5ec5680dc6
commit 038765a095
2 changed files with 3 additions and 1 deletions
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2
tools/power/x86/turbostat/turbostat.8
View File

@ -294,6 +294,8 @@ Alternatively, non-root users can be enabled to run turbostat this way:
# chmod +r /dev/cpu/*/msr
# chmod +r /dev/cpu_dma_latency
.B "turbostat "
reads hardware counters, but doesn't write them.
So it will not interfere with the OS or other programs, including

2
tools/power/x86/turbostat/turbostat.c
View File

@ -5004,7 +5004,7 @@ void print_dev_latency(void)
retval = read(fd, (void *)&value, sizeof(int));
if (retval != sizeof(int)) {
warn("read %s\n", path);
warn("read failed %s\n", path);
close(fd);
return;
}