2019-07-15 10:16:35

by Stephen Rothwell

[permalink] [raw]

Subject: [PATCH] MIPS: perf events: handle switch statement falling through warnings

---

Now that we build with -Wimplicit-fallthrough=3, some warnings are
produced in the arch/mips perf events code that are promoted to errors:

arch/mips/kernel/perf_event_mipsxx.c:792:3: error: this statement may fall through [-Werror=implicit-fallthrough=]
arch/mips/kernel/perf_event_mipsxx.c:795:3: error: this statement may fall through [-Werror=implicit-fallthrough=]
arch/mips/kernel/perf_event_mipsxx.c:798:3: error: this statement may fall through [-Werror=implicit-fallthrough=]
arch/mips/kernel/perf_event_mipsxx.c:1407:6: error: this statement may fall through [-Werror=implicit-fallthrough=]

Assume the fall throughs are deliberate amd annotate/eliminate them.

Cc: Peter Zijlstra <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Gustavo A. R. Silva <[email protected]>
Cc: Kees Cook <[email protected]>
Signed-off-by: Stephen Rothwell <[email protected]>
---
arch/mips/kernel/perf_event_mipsxx.c | 28 ++++++++++++++--------------
1 file changed, 14 insertions(+), 14 deletions(-)

I haven't even build tested this, sorry, but will add it to linux-next
tomorrow. It should be no worse than the current state :-)

diff --git a/arch/mips/kernel/perf_event_mipsxx.c b/arch/mips/kernel/perf_event_mipsxx.c
index e0ebaa0a333e..40106731e97e 100644
--- a/arch/mips/kernel/perf_event_mipsxx.c
+++ b/arch/mips/kernel/perf_event_mipsxx.c
@@ -790,15 +790,19 @@ static void reset_counters(void *arg)
case 4:
mipsxx_pmu_write_control(3, 0);
mipspmu.write_counter(3, 0);
+ /* fall through */
case 3:
mipsxx_pmu_write_control(2, 0);
mipspmu.write_counter(2, 0);
+ /* fall through */
case 2:
mipsxx_pmu_write_control(1, 0);
mipspmu.write_counter(1, 0);
+ /* fall through */
case 1:
mipsxx_pmu_write_control(0, 0);
mipspmu.write_counter(0, 0);
+ /* fall through */
}
}

@@ -1379,7 +1383,7 @@ static int mipsxx_pmu_handle_shared_irq(void)
struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
struct perf_sample_data data;
unsigned int counters = mipspmu.num_counters;
- u64 counter;
+ unsigned int n;
int handled = IRQ_NONE;
struct pt_regs *regs;

@@ -1401,20 +1405,16 @@ static int mipsxx_pmu_handle_shared_irq(void)

perf_sample_data_init(&data, 0, 0);

- switch (counters) {
-#define HANDLE_COUNTER(n) \
- case n + 1: \
- if (test_bit(n, cpuc->used_mask)) { \
- counter = mipspmu.read_counter(n); \
- if (counter & mipspmu.overflow) { \
- handle_associated_event(cpuc, n, &data, regs); \
- handled = IRQ_HANDLED; \
- } \
+ for (n = (counters > 4) ? 3 : (counters - 1); n >= 0; n--) {
+ u64 counter;
+
+ if (test_bit(n, cpuc->used_mask)) {
+ counter = mipspmu.read_counter(n);
+ if (counter & mipspmu.overflow) {
+ handle_associated_event(cpuc, n, &data, regs);
+ handled = IRQ_HANDLED;
+ }
}
- HANDLE_COUNTER(3)
- HANDLE_COUNTER(2)
- HANDLE_COUNTER(1)
- HANDLE_COUNTER(0)
}

#ifdef CONFIG_MIPS_PERF_SHARED_TC_COUNTERS
--
2.22.0

--
Cheers,
Stephen Rothwell

---

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2019-07-15 11:24:07

by Paul Burton

[permalink] [raw]

Subject: Re: [PATCH] MIPS: perf events: handle switch statement falling through warnings

---

Hello,

Stephen Rothwell wrote:
> Now that we build with -Wimplicit-fallthrough=3, some warnings are
> produced in the arch/mips perf events code that are promoted to errors:
>
> arch/mips/kernel/perf_event_mipsxx.c:792:3: error: this statement may fall through [-Werror=implicit-fallthrough=]
> arch/mips/kernel/perf_event_mipsxx.c:795:3: error: this statement may fall through [-Werror=implicit-fallthrough=]
> arch/mips/kernel/perf_event_mipsxx.c:798:3: error: this statement may fall through [-Werror=implicit-fallthrough=]
> arch/mips/kernel/perf_event_mipsxx.c:1407:6: error: this statement may fall through [-Werror=implicit-fallthrough=]
>
> Assume the fall throughs are deliberate amd annotate/eliminate them.
>
> Cc: Peter Zijlstra <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: Arnaldo Carvalho de Melo <[email protected]>
> Cc: Alexander Shishkin <[email protected]>
> Cc: Jiri Olsa <[email protected]>
> Cc: Namhyung Kim <[email protected]>
> Cc: Gustavo A. R. Silva <[email protected]>
> Cc: Kees Cook <[email protected]>
> Signed-off-by: Stephen Rothwell <[email protected]>

Applied (with some tweaks) to mips-next.

Thanks,
Paul

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