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SubjectRe: [PATCH v2 5/7] ARM: perf_event: Fully support Krait CPU PMU events
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.

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
[<c02165dc>] (unwind_backtrace) from [<c0212ffc>] (show_stack+0x10/0x14)
[<c0212ffc>] (show_stack) from [<c06ad5fc>] (dump_stack+0x6c/0xb8)
[<c06ad5fc>] (dump_stack) from [<c04b0928>] (debug_smp_processor_id+0xc4/0xe8)
[<c04b0928>] (debug_smp_processor_id) from [<c021a19c>] (krait_pmu_get_event_idx+0x58/0xd8)
[<c021a19c>] (krait_pmu_get_event_idx) from [<c021833c>] (validate_event+0x2c/0x54)
[<c021833c>] (validate_event) from [<c02186b4>] (armpmu_event_init+0x264/0x2dc)
[<c02186b4>] (armpmu_event_init) from [<c02b28e4>] (perf_init_event+0x138/0x194)
[<c02b28e4>] (perf_init_event) from [<c02b2c04>] (perf_event_alloc+0x2c4/0x348)
[<c02b2c04>] (perf_event_alloc) from [<c02b37e4>] (SyS_perf_event_open+0x7b8/0x9cc)
[<c02b37e4>] (SyS_perf_event_open) from [<c020ef80>] (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.

This is the diff for the latter version. I'll let the fuzzer run overnight.

diff --git a/arch/arm/include/asm/pmu.h b/arch/arm/include/asm/pmu.h
index 994ac445e792..ae1919be8f98 100644
--- a/arch/arm/include/asm/pmu.h
+++ b/arch/arm/include/asm/pmu.h
@@ -71,7 +71,8 @@ struct arm_pmu {
void (*disable)(struct perf_event *event);
int (*get_event_idx)(struct pmu_hw_events *hw_events,
struct perf_event *event);
- void (*clear_event_idx)(struct perf_event *event);
+ void (*clear_event_idx)(struct pmu_hw_events *hw_events,
+ struct perf_event *event);
int (*set_event_filter)(struct hw_perf_event *evt,
struct perf_event_attr *attr);
u32 (*read_counter)(struct perf_event *event);
diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c
index 70191f68c26d..361a1aaee7c8 100644
--- a/arch/arm/kernel/perf_event.c
+++ b/arch/arm/kernel/perf_event.c
@@ -208,7 +208,7 @@ armpmu_del(struct perf_event *event, int flags)
hw_events->events[idx] = NULL;
clear_bit(idx, hw_events->used_mask);
if (armpmu->clear_event_idx)
- armpmu->clear_event_idx(event);
+ armpmu->clear_event_idx(hw_events, event);

perf_event_update_userpage(event);
}
diff --git a/arch/arm/kernel/perf_event_v7.c b/arch/arm/kernel/perf_event_v7.c
index daa675529c12..1a905395b74c 100644
--- a/arch/arm/kernel/perf_event_v7.c
+++ b/arch/arm/kernel/perf_event_v7.c
@@ -1483,9 +1483,6 @@ static int armv7_a7_pmu_init(struct arm_pmu *cpu_pmu)
#define VENUM_EVENT (2 << 16)
#define KRAIT_EVENT_MASK (KRAIT_EVENT | VENUM_EVENT)
#define PMRESRn_EN BIT(31)
-#define NUM_PMRESR (KRAIT_VPMRESR0_GROUP0 + 4 - KRAIT_PMRESR0_GROUP0)
-
-static DEFINE_PER_CPU(unsigned long [BITS_TO_LONGS(NUM_PMRESR)], pmresrn_used);

static u32 krait_read_pmresrn(int n)
{
@@ -1542,6 +1539,7 @@ static void krait_pre_vpmresr0(u32 *venum_orig_val, u32 *fp_orig_val)
u32 venum_new_val;
u32 fp_new_val;

+ BUG_ON(preemptible());
/* CPACR Enable CP10 and CP11 access */
*venum_orig_val = get_copro_access();
venum_new_val = *venum_orig_val | CPACC_SVC(10) | CPACC_SVC(11);
@@ -1555,6 +1553,7 @@ static void krait_pre_vpmresr0(u32 *venum_orig_val, u32 *fp_orig_val)

static void krait_post_vpmresr0(u32 venum_orig_val, u32 fp_orig_val)
{
+ BUG_ON(preemptible());
/* Restore FPEXC */
fmxr(FPEXC, fp_orig_val);
isb();
@@ -1750,7 +1749,6 @@ static int krait_pmu_get_event_idx(struct pmu_hw_events *cpuc,
unsigned int group;
bool krait_event;
struct hw_perf_event *hwc = &event->hw;
- unsigned long *bitmap = this_cpu_ptr(pmresrn_used);

region = (hwc->config_base >> 12) & 0xf;
code = (hwc->config_base >> 4) & 0xff;
@@ -1773,26 +1771,27 @@ static int krait_pmu_get_event_idx(struct pmu_hw_events *cpuc,
bit = krait_get_pmresrn_event(region);
bit -= krait_get_pmresrn_event(0);
bit += group;
+ bit <<= 16; /* Use the upper 16 bits of the used_mask */

- if (test_and_set_bit(bit, bitmap))
+ if (test_and_set_bit(bit, cpuc->used_mask))
return -EAGAIN;
}

idx = armv7pmu_get_event_idx(cpuc, event);
if (idx < 0 && krait_event)
- clear_bit(bit, bitmap);
+ clear_bit(bit, cpuc->used_mask);

return idx;
}

-static void krait_pmu_clear_event_idx(struct perf_event *event)
+static void krait_pmu_clear_event_idx(struct pmu_hw_events *cpuc,
+ struct perf_event *event)
{
int bit;
struct hw_perf_event *hwc = &event->hw;
unsigned int region;
unsigned int group;
bool krait_event;
- unsigned long *bitmap = this_cpu_ptr(pmresrn_used);

region = (hwc->config_base >> 12) & 0xf;
group = (hwc->config_base >> 0) & 0xf;
@@ -1805,7 +1804,8 @@ static void krait_pmu_clear_event_idx(struct perf_event *event)
bit = krait_get_pmresrn_event(region);
bit -= krait_get_pmresrn_event(0);
bit += group;
- clear_bit(bit, bitmap);
+ bit <<= 16;
+ clear_bit(bit, cpuc->used_mask);
}
}

--
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