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Message-ID: <20190129231658.GH91506@google.com>
Date: Tue, 29 Jan 2019 17:16:58 -0600
From: Bjorn Helgaas <helgaas@...nel.org>
To: Arnd Bergmann <arnd@...db.de>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
Lukas Wunner <lukas@...ner.de>,
Andy Shevchenko <andy.shevchenko@...il.com>,
Tyrel Datwyler <tyreld@...ux.vnet.ibm.com>,
linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pci: ibmphp_hpc: turn semaphores into completions or
mutexes
On Mon, Dec 10, 2018 at 10:49:10PM +0100, Arnd Bergmann wrote:
> The sem_exit variable is conceptually a completion, so it should
> be called that.
>
> Similarly, the semOperations semaphore is a simple mutex, and
> can be changed into that, respectively.
>
> With both converted, the ibmphp_hpc_initvars() function is no longer
> used and can be removed.
>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
Applied to pci/hotplug for v5.1, thanks!
> ---
> drivers/pci/hotplug/ibmphp.h | 1 -
> drivers/pci/hotplug/ibmphp_core.c | 2 --
> drivers/pci/hotplug/ibmphp_hpc.c | 47 +++++++++----------------------
> 3 files changed, 14 insertions(+), 36 deletions(-)
>
> diff --git a/drivers/pci/hotplug/ibmphp.h b/drivers/pci/hotplug/ibmphp.h
> index b89f850c3a4e..e90a4ebf6550 100644
> --- a/drivers/pci/hotplug/ibmphp.h
> +++ b/drivers/pci/hotplug/ibmphp.h
> @@ -378,7 +378,6 @@ int ibmphp_add_pfmem_from_mem(struct resource_node *);
> struct bus_node *ibmphp_find_res_bus(u8);
> void ibmphp_print_test(void); /* for debugging purposes */
>
> -void ibmphp_hpc_initvars(void);
> int ibmphp_hpc_readslot(struct slot *, u8, u8 *);
> int ibmphp_hpc_writeslot(struct slot *, u8);
> void ibmphp_lock_operations(void);
> diff --git a/drivers/pci/hotplug/ibmphp_core.c b/drivers/pci/hotplug/ibmphp_core.c
> index 5752b57198e3..e04b17d81e38 100644
> --- a/drivers/pci/hotplug/ibmphp_core.c
> +++ b/drivers/pci/hotplug/ibmphp_core.c
> @@ -1312,8 +1312,6 @@ static int __init ibmphp_init(void)
>
> ibmphp_debug = debug;
>
> - ibmphp_hpc_initvars();
> -
> for (i = 0; i < 16; i++)
> irqs[i] = 0;
>
> diff --git a/drivers/pci/hotplug/ibmphp_hpc.c b/drivers/pci/hotplug/ibmphp_hpc.c
> index 752c384cbd4c..508a62a6b5f9 100644
> --- a/drivers/pci/hotplug/ibmphp_hpc.c
> +++ b/drivers/pci/hotplug/ibmphp_hpc.c
> @@ -15,13 +15,13 @@
>
> #include <linux/wait.h>
> #include <linux/time.h>
> +#include <linux/completion.h>
> #include <linux/delay.h>
> #include <linux/module.h>
> #include <linux/pci.h>
> #include <linux/init.h>
> #include <linux/mutex.h>
> #include <linux/sched.h>
> -#include <linux/semaphore.h>
> #include <linux/kthread.h>
> #include "ibmphp.h"
>
> @@ -88,10 +88,10 @@ static int to_debug = 0;
> //----------------------------------------------------------------------------
> // global variables
> //----------------------------------------------------------------------------
> -static struct mutex sem_hpcaccess; // lock access to HPC
> -static struct semaphore semOperations; // lock all operations and
> +static DEFINE_MUTEX(sem_hpcaccess); // lock access to HPC
> +static DEFINE_MUTEX(operations_mutex); // lock all operations and
> // access to data structures
> -static struct semaphore sem_exit; // make sure polling thread goes away
> +static DECLARE_COMPLETION(exit_complete); // make sure polling thread goes away
> static struct task_struct *ibmphp_poll_thread;
> //----------------------------------------------------------------------------
> // local function prototypes
> @@ -109,23 +109,6 @@ static int hpc_wait_ctlr_notworking(int, struct controller *, void __iomem *, u8
> //----------------------------------------------------------------------------
>
>
> -/*----------------------------------------------------------------------
> -* Name: ibmphp_hpc_initvars
> -*
> -* Action: initialize semaphores and variables
> -*---------------------------------------------------------------------*/
> -void __init ibmphp_hpc_initvars(void)
> -{
> - debug("%s - Entry\n", __func__);
> -
> - mutex_init(&sem_hpcaccess);
> - sema_init(&semOperations, 1);
> - sema_init(&sem_exit, 0);
> - to_debug = 0;
> -
> - debug("%s - Exit\n", __func__);
> -}
> -
> /*----------------------------------------------------------------------
> * Name: i2c_ctrl_read
> *
> @@ -780,7 +763,7 @@ void free_hpc_access(void)
> *---------------------------------------------------------------------*/
> void ibmphp_lock_operations(void)
> {
> - down(&semOperations);
> + mutex_lock(&operations_mutex);
> to_debug = 1;
> }
>
> @@ -790,7 +773,7 @@ void ibmphp_lock_operations(void)
> void ibmphp_unlock_operations(void)
> {
> debug("%s - Entry\n", __func__);
> - up(&semOperations);
> + mutex_unlock(&operations_mutex);
> to_debug = 0;
> debug("%s - Exit\n", __func__);
> }
> @@ -816,7 +799,7 @@ static int poll_hpc(void *data)
>
> while (!kthread_should_stop()) {
> /* try to get the lock to do some kind of hardware access */
> - down(&semOperations);
> + mutex_lock(&operations_mutex);
>
> switch (poll_state) {
> case POLL_LATCH_REGISTER:
> @@ -871,13 +854,13 @@ static int poll_hpc(void *data)
> break;
> case POLL_SLEEP:
> /* don't sleep with a lock on the hardware */
> - up(&semOperations);
> + mutex_unlock(&operations_mutex);
> msleep(POLL_INTERVAL_SEC * 1000);
>
> if (kthread_should_stop())
> goto out_sleep;
>
> - down(&semOperations);
> + mutex_lock(&operations_mutex);
>
> if (poll_count >= POLL_LATCH_CNT) {
> poll_count = 0;
> @@ -887,12 +870,12 @@ static int poll_hpc(void *data)
> break;
> }
> /* give up the hardware semaphore */
> - up(&semOperations);
> + mutex_unlock(&operations_mutex);
> /* sleep for a short time just for good measure */
> out_sleep:
> msleep(100);
> }
> - up(&sem_exit);
> + complete(&exit_complete);
> debug("%s - Exit\n", __func__);
> return 0;
> }
> @@ -1060,9 +1043,9 @@ void __exit ibmphp_hpc_stop_poll_thread(void)
> debug("after locking operations\n");
>
> // wait for poll thread to exit
> - debug("before sem_exit down\n");
> - down(&sem_exit);
> - debug("after sem_exit down\n");
> + debug("before exit_complete down\n");
> + wait_for_completion(&exit_complete);
> + debug("after exit_completion down\n");
>
> // cleanup
> debug("before free_hpc_access\n");
> @@ -1070,8 +1053,6 @@ void __exit ibmphp_hpc_stop_poll_thread(void)
> debug("after free_hpc_access\n");
> ibmphp_unlock_operations();
> debug("after unlock operations\n");
> - up(&sem_exit);
> - debug("after sem exit up\n");
>
> debug("%s - Exit\n", __func__);
> }
> --
> 2.20.0
>
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