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From: "André Almeida" <andrealmeid@collabora.com>
To: Alistair Francis <alistair.francis@opensource.wdc.com>
Cc: linux-kernel@vger.kernel.org, alistair23@gmail.com,
	linux-riscv@lists.infradead.org, namhyung@kernel.org,
	jolsa@redhat.com, linux-perf-users@vger.kernel.org,
	alexander.shishkin@linux.intel.com, mark.rutland@arm.com,
	acme@kernel.org, dave@stgolabs.net, dvhart@infradead.org,
	peterz@infradead.org, mingo@redhat.com, tglx@linutronix.de,
	atish.patra@wdc.com, arnd@arndb.de,
	Alistair Francis <alistair.francis@wdc.com>
Subject: Re: [PATCH v3 2/2] perf bench: Add support for 32-bit systems with 64-bit time_t
Date: Mon, 20 Sep 2021 19:47:44 -0300	[thread overview]
Message-ID: <72990864-5ec6-1f73-efd9-61b667a172dd@collabora.com> (raw)
In-Reply-To: <20210917061040.2270822-2-alistair.francis@opensource.wdc.com>

Hi Alistair,

Às 03:10 de 17/09/21, Alistair Francis escreveu:
> From: Alistair Francis <alistair.francis@wdc.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.
> 

Thanks for your patch! However, I don't think that any futex operation
at perf has timeout. Do you plan to implement a test that use it? Or the
idea is to get this ready for it in case someone want to do so in the
future?


Also, I faced a similar problem with the new futex2 syscalls, that
supports exclusively 64bit timespec. But I took a different approach: I
called __NR_clock_gettime64 for 32bit architectures so it wouldn't
require to convert the struct:

#if defined(__i386__) || __TIMESIZE == 32
# define NR_gettime64 __NR_clock_gettime64
#else
# define NR_gettime64 __NR_clock_gettime
#endif

struct timespec64 {
	long long tv_sec;	/* seconds */
	long long tv_nsec;	/* nanoseconds */
};

int gettime64(clock_t clockid, struct timespec64 *tv)
{
	return syscall(NR_gettime64, clockid, tv);
}

Then we can just use &timeout at __NR_futex_time64 for 32bit arch and at
__NR_futex for 64bit arch.

This might be a simpler solution to the problem that you are facing but
I'm not entirely sure. Also, futex's selftests do use the timeout
argument and I think that they also won't compile in 32-bit RISC-V, so
maybe we can start from there so we can actually test the timeout
argument and check if it's working.

Thanks,
	André

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linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

WARNING: multiple messages have this Message-ID
From: "André Almeida" <andrealmeid@collabora.com>
To: Alistair Francis <alistair.francis@opensource.wdc.com>
Cc: linux-kernel@vger.kernel.org, alistair23@gmail.com,
	linux-riscv@lists.infradead.org, namhyung@kernel.org,
	jolsa@redhat.com, linux-perf-users@vger.kernel.org,
	alexander.shishkin@linux.intel.com, mark.rutland@arm.com,
	acme@kernel.org, dave@stgolabs.net, dvhart@infradead.org,
	peterz@infradead.org, mingo@redhat.com, tglx@linutronix.de,
	atish.patra@wdc.com, arnd@arndb.de,
	Alistair Francis <alistair.francis@wdc.com>
Subject: Re: [PATCH v3 2/2] perf bench: Add support for 32-bit systems with 64-bit time_t
Date: Mon, 20 Sep 2021 19:47:44 -0300	[thread overview]
Message-ID: <72990864-5ec6-1f73-efd9-61b667a172dd@collabora.com> (raw)
In-Reply-To: <20210917061040.2270822-2-alistair.francis@opensource.wdc.com>

Hi Alistair,

Às 03:10 de 17/09/21, Alistair Francis escreveu:
> From: Alistair Francis <alistair.francis@wdc.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.
> 

Thanks for your patch! However, I don't think that any futex operation
at perf has timeout. Do you plan to implement a test that use it? Or the
idea is to get this ready for it in case someone want to do so in the
future?


Also, I faced a similar problem with the new futex2 syscalls, that
supports exclusively 64bit timespec. But I took a different approach: I
called __NR_clock_gettime64 for 32bit architectures so it wouldn't
require to convert the struct:

#if defined(__i386__) || __TIMESIZE == 32
# define NR_gettime64 __NR_clock_gettime64
#else
# define NR_gettime64 __NR_clock_gettime
#endif

struct timespec64 {
	long long tv_sec;	/* seconds */
	long long tv_nsec;	/* nanoseconds */
};

int gettime64(clock_t clockid, struct timespec64 *tv)
{
	return syscall(NR_gettime64, clockid, tv);
}

Then we can just use &timeout at __NR_futex_time64 for 32bit arch and at
__NR_futex for 64bit arch.

This might be a simpler solution to the problem that you are facing but
I'm not entirely sure. Also, futex's selftests do use the timeout
argument and I think that they also won't compile in 32-bit RISC-V, so
maybe we can start from there so we can actually test the timeout
argument and check if it's working.

Thanks,
	André

  parent reply	other threads:[~2021-09-20 22:48 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-17  6:10 [PATCH v3 1/2] perf benchmark: Call the futex syscall from a function Alistair Francis
2021-09-17  6:10 ` Alistair Francis
2021-09-17  6:10 ` [PATCH v3 2/2] perf bench: Add support for 32-bit systems with 64-bit time_t Alistair Francis
2021-09-17  6:10   ` Alistair Francis
2021-09-17  7:33   ` Arnd Bergmann
2021-09-17  7:33     ` Arnd Bergmann
2021-09-17 18:33   ` Davidlohr Bueso
2021-09-17 18:33     ` Davidlohr Bueso
2021-09-20 22:47   ` André Almeida [this message]
2021-09-20 22:47     ` André Almeida
2021-09-21  8:08     ` Arnd Bergmann
2021-09-21  8:08       ` Arnd Bergmann
2021-09-21 23:06       ` André Almeida
2021-09-21 23:06         ` André Almeida
2021-09-22 11:26         ` Arnd Bergmann
2021-09-22 11:26           ` Arnd Bergmann
2021-09-22 11:27         ` Arnd Bergmann
2021-09-22 11:27           ` Arnd Bergmann
2021-09-24  4:34       ` Alistair Francis
2021-09-24  4:34         ` Alistair Francis
2021-09-24  4:34     ` Alistair Francis
2021-09-24  4:34       ` Alistair Francis
2021-09-26 21:32       ` André Almeida
2021-09-26 21:32         ` André Almeida
2021-09-17 18:21 ` [PATCH v3 1/2] perf benchmark: Call the futex syscall from a function Davidlohr Bueso
2021-09-17 18:21   ` Davidlohr Bueso

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