diff options
author | Michael Neuling <mikey@neuling.org> | 2012-10-26 18:28:56 +0200 |
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committer | Ingo Molnar <mingo@kernel.org> | 2012-10-30 10:07:58 +0100 |
commit | 0d855354ea351bec6b222e9fea86a876cfafdcb6 (patch) | |
tree | a17fa24e9d5a30fec1c8d17896acd10b5d161d45 /tools | |
parent | 35fd3dc58da675d659513384221349ef90749a01 (diff) | |
download | linux-0d855354ea351bec6b222e9fea86a876cfafdcb6.tar.bz2 |
perf, powerpc: Fix hw breakpoints returning -ENOSPC
I've been trying to get hardware breakpoints with perf to work
on POWER7 but I'm getting the following:
% perf record -e mem:0x10000000 true
Error: sys_perf_event_open() syscall returned with 28 (No space left on device). /bin/dmesg may provide additional information.
Fatal: No CONFIG_PERF_EVENTS=y kernel support configured?
true: Terminated
(FWIW adding -a and it works fine)
Debugging it seems that __reserve_bp_slot() is returning ENOSPC
because it thinks there are no free breakpoint slots on this
CPU.
I have a 2 CPUs, so perf userspace is doing two perf_event_open
syscalls to add a counter to each CPU [1]. The first syscall
succeeds but the second is failing.
On this second syscall, fetch_bp_busy_slots() sets slots.pinned
to be 1, despite there being no breakpoint on this CPU. This is
because the call the task_bp_pinned, checks all CPUs, rather
than just the current CPU. POWER7 only has one hardware
breakpoint per CPU (ie. HBP_NUM=1), so we return ENOSPC.
The following patch fixes this by checking the associated CPU
for each breakpoint in task_bp_pinned. I'm not familiar with
this code, so it's provided as a reference to the above issue.
Signed-off-by: Michael Neuling <mikey@neuling.org>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Michael Ellerman <michael@ellerman.id.au>
Cc: Jovi Zhang <bookjovi@gmail.com>
Cc: K Prasad <prasad@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1351268936-2956-1-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'tools')
0 files changed, 0 insertions, 0 deletions