From: Michael Neuling Date: Fri, 26 Oct 2012 16:28:56 +0000 (+0200) Subject: perf, powerpc: Fix hw breakpoints returning -ENOSPC X-Git-Tag: v3.7-rc8~12^2~2 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0d855354ea351bec6b222e9fea86a876cfafdcb6;p=pandora-kernel.git 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 Acked-by: Peter Zijlstra Cc: Michael Ellerman Cc: Jovi Zhang Cc: K Prasad Link: http://lkml.kernel.org/r/1351268936-2956-1-git-send-email-fweisbec@gmail.com Signed-off-by: Ingo Molnar --- Reading git-diff-tree failed