diff options
Diffstat (limited to 'arch/powerpc')
| -rw-r--r-- | arch/powerpc/oprofile/op_model_power4.c | 24 |
1 files changed, 23 insertions, 1 deletions
diff --git a/arch/powerpc/oprofile/op_model_power4.c b/arch/powerpc/oprofile/op_model_power4.c index 8ee51a252cf1..e6bec74be131 100644 --- a/arch/powerpc/oprofile/op_model_power4.c +++ b/arch/powerpc/oprofile/op_model_power4.c @@ -261,6 +261,28 @@ static int get_kernel(unsigned long pc, unsigned long mmcra) return is_kernel; } +static bool pmc_overflow(unsigned long val) +{ + if ((int)val < 0) + return true; + + /* + * Events on POWER7 can roll back if a speculative event doesn't + * eventually complete. Unfortunately in some rare cases they will + * raise a performance monitor exception. We need to catch this to + * ensure we reset the PMC. In all cases the PMC will be 256 or less + * cycles from overflow. + * + * We only do this if the first pass fails to find any overflowing + * PMCs because a user might set a period of less than 256 and we + * don't want to mistakenly reset them. + */ + if (__is_processor(PV_POWER7) && ((0x80000000 - val) <= 256)) + return true; + + return false; +} + static void power4_handle_interrupt(struct pt_regs *regs, struct op_counter_config *ctr) { @@ -281,7 +303,7 @@ static void power4_handle_interrupt(struct pt_regs *regs, for (i = 0; i < cur_cpu_spec->num_pmcs; ++i) { val = classic_ctr_read(i); - if (val < 0) { + if (pmc_overflow(val)) { if (oprofile_running && ctr[i].enabled) { oprofile_add_ext_sample(pc, regs, i, is_kernel); classic_ctr_write(i, reset_value[i]); |