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Date: Thu, 21 Jul 2016 15:43:30 +0200
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Lv Zheng <lv.zheng@...el.com>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
Len Brown <len.brown@...el.com>, Lv Zheng <zetalog@...il.com>,
linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org
Subject: Re: [PATCH v2 1/2] ACPI / debugger: Add kernel flushing support
On Tuesday, July 19, 2016 06:00:39 PM Lv Zheng wrote:
> This patch adds debugger log flushing support in kernel via .ioctl()
> callback. The in-kernel flushing is more efficient, because it reduces
> useless log IOs by bypassing log user_read/kern_write during the flush
> period.
>
> Signed-off-by: Lv Zheng <lv.zheng@...el.com>
Overall, this is an optimization, right?
So is adding a new IOCTL really worth it?
> ---
> drivers/acpi/acpi_dbg.c | 98 +++++++++++++++++++++++++++++++++++++++++--
> include/linux/acpi-ioctls.h | 21 ++++++++++
> 2 files changed, 115 insertions(+), 4 deletions(-)
> create mode 100644 include/linux/acpi-ioctls.h
>
> diff --git a/drivers/acpi/acpi_dbg.c b/drivers/acpi/acpi_dbg.c
> index dee8692..6ac1388 100644
> --- a/drivers/acpi/acpi_dbg.c
> +++ b/drivers/acpi/acpi_dbg.c
> @@ -22,6 +22,7 @@
> #include <linux/debugfs.h>
> #include <linux/circ_buf.h>
> #include <linux/acpi.h>
> +#include <linux/acpi-ioctls.h>
That should go into the uapi directory at least.
> #include "internal.h"
>
> #define ACPI_AML_BUF_ALIGN (sizeof (acpi_size))
> @@ -46,6 +47,8 @@
> #define ACPI_AML_KERN (ACPI_AML_IN_KERN | ACPI_AML_OUT_KERN)
> #define ACPI_AML_BUSY (ACPI_AML_USER | ACPI_AML_KERN)
> #define ACPI_AML_OPEN (ACPI_AML_OPENED | ACPI_AML_CLOSED)
> +#define ACPI_AML_FLUSHING_LOG 0x0040 /* flushing log output */
> +#define ACPI_AML_WAITING_CMD 0x0080 /* waiting for cmd input */
>
> struct acpi_aml_io {
> wait_queue_head_t wait;
> @@ -120,6 +123,20 @@ static inline bool __acpi_aml_busy(void)
> return false;
> }
>
> +static inline bool __acpi_aml_waiting_cmd(void)
> +{
> + if (acpi_aml_io.flags & ACPI_AML_WAITING_CMD)
> + return true;
> + return false;
Oh well.
What about
return !!(acpi_aml_io.flags & ACPI_AML_WAITING_CMD);
> +}
> +
> +static inline bool __acpi_aml_flushing_log(void)
> +{
> + if (acpi_aml_io.flags & ACPI_AML_FLUSHING_LOG)
> + return true;
> + return false;
And analogously here?
> +}
> +
> static inline bool __acpi_aml_opened(void)
> {
> if (acpi_aml_io.flags & ACPI_AML_OPEN)
> @@ -152,6 +169,26 @@ static bool acpi_aml_busy(void)
> return ret;
> }
>
> +static inline bool acpi_aml_waiting_cmd(void)
> +{
> + bool ret;
> +
> + mutex_lock(&acpi_aml_io.lock);
> + ret = __acpi_aml_waiting_cmd();
> + mutex_unlock(&acpi_aml_io.lock);
> + return ret;
> +}
> +
> +static inline bool acpi_aml_flushing_log(void)
> +{
> + bool ret;
> +
> + mutex_lock(&acpi_aml_io.lock);
> + ret = __acpi_aml_flushing_log();
> + mutex_unlock(&acpi_aml_io.lock);
> + return ret;
> +}
> +
> static bool acpi_aml_used(void)
> {
> bool ret;
> @@ -183,7 +220,8 @@ static bool acpi_aml_kern_writable(void)
>
> mutex_lock(&acpi_aml_io.lock);
> ret = !__acpi_aml_access_ok(ACPI_AML_OUT_KERN) ||
> - __acpi_aml_writable(&acpi_aml_io.out_crc, ACPI_AML_OUT_KERN);
> + __acpi_aml_writable(&acpi_aml_io.out_crc, ACPI_AML_OUT_KERN) ||
> + __acpi_aml_flushing_log();
> mutex_unlock(&acpi_aml_io.lock);
> return ret;
> }
> @@ -264,6 +302,9 @@ static int acpi_aml_write_kern(const char *buf, int len)
> int n;
> char *p;
>
> + if (acpi_aml_flushing_log())
> + return len;
> +
> ret = acpi_aml_lock_write(crc, ACPI_AML_OUT_KERN);
> if (ret < 0)
> return ret;
> @@ -458,9 +499,18 @@ static int acpi_aml_wait_command_ready(bool single_step,
> else
> acpi_os_printf("\n%1c ", ACPI_DEBUGGER_COMMAND_PROMPT);
>
> + mutex_lock(&acpi_aml_io.lock);
> + acpi_aml_io.flags |= ACPI_AML_WAITING_CMD;
> + wake_up_interruptible(&acpi_aml_io.wait);
> + mutex_unlock(&acpi_aml_io.lock);
> +
> status = acpi_os_get_line(buffer, length, NULL);
> if (ACPI_FAILURE(status))
> return -EINVAL;
> +
> + mutex_lock(&acpi_aml_io.lock);
> + acpi_aml_io.flags &= ~ACPI_AML_WAITING_CMD;
> + mutex_unlock(&acpi_aml_io.lock);
> return 0;
> }
>
> @@ -593,9 +643,11 @@ static int acpi_aml_read_user(char __user *buf, int len)
> smp_rmb();
> p = &crc->buf[crc->tail];
> n = min(len, circ_count_to_end(crc));
> - if (copy_to_user(buf, p, n)) {
> - ret = -EFAULT;
> - goto out;
> + if (!acpi_aml_flushing_log()) {
> + if (copy_to_user(buf, p, n)) {
> + ret = -EFAULT;
> + goto out;
> + }
> }
> /* sync tail after removing logs */
> smp_mb();
> @@ -731,10 +783,48 @@ static unsigned int acpi_aml_poll(struct file *file, poll_table *wait)
> return masks;
> }
>
> +static int acpi_aml_flush(void)
> +{
> + int ret;
> +
> + /*
> + * Discard output buffer and put the driver into a state waiting
> + * for the new user input.
> + */
> + mutex_lock(&acpi_aml_io.lock);
> + acpi_aml_io.flags |= ACPI_AML_FLUSHING_LOG;
> + mutex_unlock(&acpi_aml_io.lock);
> +
> + ret = wait_event_interruptible(acpi_aml_io.wait,
> + acpi_aml_waiting_cmd());
> + (void)acpi_aml_read_user(NULL, ACPI_AML_BUF_SIZE);
> +
> + mutex_lock(&acpi_aml_io.lock);
> + acpi_aml_io.flags &= ~ACPI_AML_FLUSHING_LOG;
> + mutex_unlock(&acpi_aml_io.lock);
> + return ret;
> +}
> +
> +static long acpi_aml_ioctl(struct file *file,
> + unsigned int cmd, unsigned long arg)
> +{
> + long ret = -EINVAL;
> +
> + switch (cmd) {
> + case ACPI_IOCTL_DEBUGGER_FLUSH:
> + ret = acpi_aml_flush();
> + break;
> + default:
> + break;
> + }
> + return ret;
return cmd == ACPI_IOCTL_DEBUGGER_FLUSH ? acpi_aml_flush() : -EINVAL;
> +}
> +
> static const struct file_operations acpi_aml_operations = {
> .read = acpi_aml_read,
> .write = acpi_aml_write,
> .poll = acpi_aml_poll,
> + .unlocked_ioctl = acpi_aml_ioctl,
> .open = acpi_aml_open,
> .release = acpi_aml_release,
> .llseek = generic_file_llseek,
> diff --git a/include/linux/acpi-ioctls.h b/include/linux/acpi-ioctls.h
> new file mode 100644
> index 0000000..56b8170
> --- /dev/null
> +++ b/include/linux/acpi-ioctls.h
include/uapi/linux/
> @@ -0,0 +1,21 @@
> +/*
> + * ACPI IOCTL collections
> + *
> + * Copyright (C) 2016, Intel Corporation
> + * Authors: Lv Zheng <lv.zheng@...el.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#ifndef _LINUX_ACPI_IOCTLS_H
> +#define _LINUX_ACPI_IOCTLS_H
> +
> +#include <linux/ioctl.h>
> +
> +#define ACPI_IOCTL_IDENT 'a'
> +
> +#define ACPI_IOCTL_DEBUGGER_FLUSH _IO(ACPI_IOCTL_IDENT, 0x80)
> +
> +#endif /* _LINUX_ACPI_IOCTLS_H */
>
Plus patches that change the ABI should be CCed to the ABI review list for,
well, review.
Thanks,
Rafael
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