linux-kernel - Re: [PATCH v5 1/6] perf bench futex: Add support for 32-bit systems with 64-bit time

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Message-ID: <YbNSRcSrAaurqDEv@kernel.org>
Date:   Fri, 10 Dec 2021 10:12:37 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Alistair Francis <alistair.francis@...nsource.wdc.com>,
        Arnd Bergmann <arnd@...db.de>, Davidlohr Bueso <dbueso@...e.de>
Cc:     linux-kernel@...r.kernel.org, dave@...olabs.net,
        dvhart@...radead.org, alistair23@...il.com,
        Namhyung Kim <namhyung@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>, linux-perf-users@...r.kernel.org,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Mark Rutland <mark.rutland@....com>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Alistair Francis <alistair.francis@....com>,
        Atish Patra <atish.patra@....com>,
        linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v5 1/6] perf bench futex: Add support for 32-bit systems
 with 64-bit time_t

Em Fri, Dec 10, 2021 at 09:58:52AM +1000, Alistair Francis escreveu:
> From: Alistair Francis <alistair.francis@....com>
> 
> Some 32-bit architectures (such are 32-bit RISC-V) only have a 64-bit
> time_t and as such don't have the SYS_futex syscall. This patch will
> allow us to use the SYS_futex_time64 syscall on those platforms.
> 
> This also converts the futex calls to be y2038 safe (when built for a
> 5.1+ kernel).
> 
> This is a revert of commit ba4026b09d83acf56c040b6933eac7916c27e728
> "Revert "perf bench futex: Add support for 32-bit systems with 64-bit time_t"".
> 
> The original commit was reverted as including linux/time_types.h would
> fail to compile on older kernels. This commit doesn't include
> linux/time_types.h to avoid this issue.

The reverted commit had:

    Reviewed-by: Arnd Bergmann <arnd@...db.de>
    Acked-by: Davidlohr Bueso <dbueso@...e.de>

Does that stands for this new patch?

Thanks,

- Arnaldo
 
> Signed-off-by: Alistair Francis <alistair.francis@....com>
> Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
> Cc: Alistair Francis <alistair23@...il.com>
> Cc: Atish Patra <atish.patra@....com>
> Cc: Darren Hart <dvhart@...radead.org>
> Cc: Davidlohr Bueso <dave@...olabs.net>
> Cc: Jiri Olsa <jolsa@...hat.com>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Namhyung Kim <namhyung@...nel.org>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: linux-riscv@...ts.infradead.org
> Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
> Reviewed-by: Arnd Bergmann <arnd@...db.de>
> ---
>  tools/perf/bench/futex.h | 52 +++++++++++++++++++++++++++++++++++++---
>  1 file changed, 49 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/perf/bench/futex.h b/tools/perf/bench/futex.h
> index ebdc2b032afc..385d2bdfaa9f 100644
> --- a/tools/perf/bench/futex.h
> +++ b/tools/perf/bench/futex.h
> @@ -8,6 +8,7 @@
>  #ifndef _FUTEX_H
>  #define _FUTEX_H
>  
> +#include <errno.h>
>  #include <unistd.h>
>  #include <sys/syscall.h>
>  #include <sys/types.h>
> @@ -28,7 +29,17 @@ struct bench_futex_parameters {
>  };
>  
>  /**
> - * futex_syscall() - SYS_futex syscall wrapper
> + * This is copied from linux/time_types.h.
> + * We copy this here to avoid compilation failures when running
> + * on systems that don't ship with linux/time_types.h.
> + */
> +struct __kernel_old_timespec {
> +	__kernel_old_time_t	tv_sec;		/* seconds */
> +	long			tv_nsec;	/* nanoseconds */
> +};
> +
> +/**
> + * futex_syscall() - __NR_futex syscall wrapper
>   * @uaddr:	address of first futex
>   * @op:		futex op code
>   * @val:	typically expected value of uaddr, but varies by op
> @@ -49,14 +60,49 @@ static inline int
>  futex_syscall(volatile u_int32_t *uaddr, int op, u_int32_t val, struct timespec *timeout,
>  	      volatile u_int32_t *uaddr2, int val3, int opflags)
>  {
> -	return syscall(SYS_futex, uaddr, op | opflags, val, timeout, uaddr2, val3);
> +#if defined(__NR_futex_time64)
> +	if (sizeof(*timeout) != sizeof(struct __kernel_old_timespec)) {
> +		int ret = syscall(__NR_futex_time64, uaddr, op | opflags, val, timeout,
> +				  uaddr2, val3);
> +	if (ret == 0 || errno != ENOSYS)
> +		return ret;
> +	}
> +#endif
> +
> +#if defined(__NR_futex)
> +	if (sizeof(*timeout) == sizeof(struct __kernel_old_timespec))
> +		return syscall(__NR_futex, uaddr, op | opflags, val, timeout, uaddr2, val3);
> +
> +	if (timeout && timeout->tv_sec == (long)timeout->tv_sec) {
> +		struct __kernel_old_timespec ts32;
> +
> +		ts32.tv_sec = (__kernel_long_t) timeout->tv_sec;
> +		ts32.tv_nsec = (__kernel_long_t) timeout->tv_nsec;
> +
> +		return syscall(__NR_futex, uaddr, op | opflags, val, ts32, uaddr2, val3);
> +	} else if (!timeout) {
> +		return syscall(__NR_futex, uaddr, op | opflags, val, NULL, uaddr2, val3);
> +	}
> +#endif
> +
> +	errno = ENOSYS;
> +	return -1;
>  }
>  
>  static inline int
>  futex_syscall_nr_requeue(volatile u_int32_t *uaddr, int op, u_int32_t val, int nr_requeue,
>  			 volatile u_int32_t *uaddr2, int val3, int opflags)
>  {
> -	return syscall(SYS_futex, uaddr, op | opflags, val, nr_requeue, uaddr2, val3);
> +#if defined(__NR_futex_time64)
> +	int ret =  syscall(__NR_futex_time64, uaddr, op | opflags, val, nr_requeue,
> +			   uaddr2, val3);
> +	if (ret == 0 || errno != ENOSYS)
> +		return ret;
> +#endif
> +
> +#if defined(__NR_futex)
> +	return syscall(__NR_futex, uaddr, op | opflags, val, nr_requeue, uaddr2, val3);
> +#endif
>  }
>  
>  /**
> -- 
> 2.31.1

-- 

- Arnaldo