mirror of
https://github.com/hardkernel/linux.git
synced 2026-06-06 19:08:57 +09:00
9d48c7afed
When a CPU is hotplugged while the perf stat -e cycles command is
running, a wrong (very large) value is displayed immediately after the
CPU removal:
Check the values, shouldn't be too high as in
time counts unit events
1.001101919 29261846 cycles
2.002454499 17523405 cycles
3.003659292 24361161 cycles
4.004816983 18446744073638406144 cycles
5.005671647 <not counted> cycles
...
The CPU hotplug off took place after 3 seconds.
The issue is the read of the event count value after 4 seconds when
the CPU is not available and the read of the counter returns an
error. This is treated as a counter value of zero. This results
in a very large value (0 - previous_value).
Fix this by detecting the hotplugged off CPU and report 0 instead
of a very large number.
Cc: stable@vger.kernel.org
Fixes: a029a4eab3 ("s390/cpumf: Allow concurrent access for CPU Measurement Counter Facility")
Reported-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Reviewed-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.