The kernel build with CONFIG_OPROFILE and CPU_HOTPLUG enabled.
The oprofile is initialised using system timer in absence of hardware
counters supports. Oprofile isn't started from userland.
In this setup while doing a CPU offline the kernel hangs in infinite
for loop inside lock_hrtimer_base() function
This happens because as part of oprofile_cpu_notify(, it tries to
stop an hrtimer which was never started. These per-cpu hrtimers
are started when the oprfile is started.
echo 1 > /dev/oprofile/enable
This problem also existwhen the cpu is booted with maxcpus parameter
set. When bringing the remaining cpus online the timers are started
even if oprofile is not yet enabled.
This patch fix this issue by adding a state variable so that
these hrtimer start/stop is only attempted when oprofile is
started
For stable kernels v2.6.35.y and v2.6.36.y.
Reported-by: Jan Sebastien <s-jan@ti.com>
Tested-by: sricharan <r.sricharan@ti.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Cc: stable@kernel.org
Signed-off-by: Robert Richter <robert.richter@amd.com>
Oprofile is currently broken on systems running with NOHZ enabled.
A maximum of 1 tick is accounted via the timer_hook if a cpu sleeps
for a longer period of time. This does bad things to the percentages
in the profiler output. To solve this problem convert oprofile to
use a restarting hrtimer instead of the timer_hook.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Robert Richter <robert.richter@amd.com>
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Santosh Shilimkar
Martin Schwidefsky
Robert Richter
Linus Torvalds