From mboxrd@z Thu Jan 1 00:00:00 1970 From: will.deacon@arm.com (Will Deacon) Date: Wed, 22 Jan 2014 10:58:40 +0000 Subject: [PATCH v2 5/7] ARM: perf_event: Fully support Krait CPU PMU events In-Reply-To: <52DEEDDA.4060302@codeaurora.org> References: <1389808535-23852-1-git-send-email-sboyd@codeaurora.org> <1389808535-23852-6-git-send-email-sboyd@codeaurora.org> <20140121180711.GN30706@mudshark.cambridge.arm.com> <52DEBE6B.7000904@codeaurora.org> <52DEEDDA.4060302@codeaurora.org> Message-ID: <20140122105840.GD1621@mudshark.cambridge.arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tue, Jan 21, 2014 at 09:59:54PM +0000, Stephen Boyd wrote: > On 01/21/14 10:37, Stephen Boyd wrote: > > On 01/21/14 10:07, Will Deacon wrote: > >> Finally, I'd really like to see this get some test coverage, but I don't > >> want to try running mainline on my phone :) Could you give your patches a > >> spin with Vince's perf fuzzer please? > >> > >> https://github.com/deater/perf_event_tests.git > >> > >> (then build the contents of the fuzzer directory and run it for as long as > >> you can). > >> > > Ok. I'll see what I can do. > > Neat. This quickly discovered a problem. Yeah, the fuzzer is good at that! > BUG: using smp_processor_id() in preemptible [00000000] code: perf_fuzzer/70 > caller is krait_pmu_get_event_idx+0x58/0xd8 > CPU: 2 PID: 70 Comm: perf_fuzzer Not tainted 3.13.0-rc7-next-20140108-00041-gb038353c8516-dirty #58 > [] (unwind_backtrace) from [] (show_stack+0x10/0x14) > [] (show_stack) from [] (dump_stack+0x6c/0xb8) > [] (dump_stack) from [] (debug_smp_processor_id+0xc4/0xe8) > [] (debug_smp_processor_id) from [] (krait_pmu_get_event_idx+0x58/0xd8) > [] (krait_pmu_get_event_idx) from [] (validate_event+0x2c/0x54) > [] (validate_event) from [] (armpmu_event_init+0x264/0x2dc) > [] (armpmu_event_init) from [] (perf_init_event+0x138/0x194) > [] (perf_init_event) from [] (perf_event_alloc+0x2c4/0x348) > [] (perf_event_alloc) from [] (SyS_perf_event_open+0x7b8/0x9cc) > [] (SyS_perf_event_open) from [] (ret_fast_syscall+0x0/0x48) > > This is happening because the pmresrn_used mask is per-cpu but > validate_group() is called in preemptible context. It looks like we'll > need to add another unsigned long * field to struct pmu_hw_events just > for Krait purposes? Or we could use the upper 16 bits of the used_mask > bitmap to hold the pmresr_used values? Sounds sort of hacky but it > avoids adding another bitmap for every PMU user and there aren't any > Krait CPUs with more than 5 counters anyway. I'm fine with that approach, but a comment saying what we're doing with those upper bits wouldn't go amiss. > This is the diff for the latter version. I'll let the fuzzer run overnight. Cheers, Will