From: David S. Miller Date: Thu, 25 Jun 2015 13:01:10 +0000 (-0700) Subject: Merge branch 'sparc-perf-stack' X-Git-Tag: v4.2-rc1~119^2 X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=f01cae4e1a9bc845ee125cdb763ccf18298d3fdc;p=karo-tx-linux.git Merge branch 'sparc-perf-stack' David Ahern says: ==================== sparc64: perf fixes for userspace stacks Coming back to the perf userspace callchain problem. As a reminder there are a series of problems trying to use perf to collect callchains with scheduling tracepoints, e.g., perf sched record -g -- . The first patch disables pagefaults while walking the user stack. As discussed a couple of months ago this is the right fix, but I was puzzled as to why processes were terminating with sigbus (and sometimes sigsegv). I believe the root of this problem is bad addresses trying to walk the frames using frame pointers. The bad addresses lead to faults that get handled by do_sparc64_fault and it aborts the task though I am still puzzled as to why it gets past this check in do_sparc64_fault: if (in_atomic() || !mm) goto intr_or_no_mm; pagefault_disable bumps the preempt_count which should make in_atomic return != 0 (building kernels with preemption set to voluntar, CONFIG_PREEMPT_VOLUNTARY=y). While this set does not fully solve the problem it does prevent a number of pain points with the current code, most notably able to lock up the system. ==================== Signed-off-by: David S. Miller --- f01cae4e1a9bc845ee125cdb763ccf18298d3fdc