[PATCH 1/2] Add mutex around semaphore counting (LP:#1017388)

[Alex Hung]

On 07/17/2012 02:08 AM, Colin King wrote:
> From: Colin Ian King <colin.king at canonical.com>
>
> The ACPICA core can execute control methods in a non
> serialized manner, so we should add a mutex lock around
> the semaphore counting mechanism to remove any race
> conditions.  This fixes bug LP:#1017388
>
> Signed-off-by: Colin Ian King <colin.king at canonical.com>
> ---
>   src/acpica/fwts_acpica.c |   16 ++++++++++++++++
>   1 file changed, 16 insertions(+)
>
> diff --git a/src/acpica/fwts_acpica.c b/src/acpica/fwts_acpica.c
> index b8119cb..cf9a4fe 100644
> --- a/src/acpica/fwts_acpica.c
> +++ b/src/acpica/fwts_acpica.c
> @@ -29,6 +29,9 @@
>   #include <errno.h>
>   #include <semaphore.h>
>   #include <signal.h>
> +#include <pthread.h>
> +
> +static pthread_mutex_t mutex_lock_count;
>
>   #include "fwts.h"
>
> @@ -109,10 +112,14 @@ void fwts_acpica_sem_count_clear(void)
>   {
>   	int i;
>
> +	pthread_mutex_lock(&mutex_lock_count);
> +
>   	for (i=0;i<MAX_SEMAPHORES;i++) {
>   		sem_hash_table[i].sem = NULL;
>   		sem_hash_table[i].count = 0;
>   	}
> +
> +	pthread_mutex_unlock(&mutex_lock_count);
>   }
>
>   /*
> @@ -171,9 +178,12 @@ static unsigned int hash_sem_handle(sem_t *sem)
>   static void hash_sem_inc_count(sem_t *sem)
>   {
>   	unsigned int i = hash_sem_handle(sem);
> +
>   	if (i != HASH_FULL) {
> +		pthread_mutex_lock(&mutex_lock_count);
>   		sem_hash_table[i].sem = sem;
>   		sem_hash_table[i].count++;
> +		pthread_mutex_unlock(&mutex_lock_count);
>   	}
>   }
>
> @@ -184,9 +194,12 @@ static void hash_sem_inc_count(sem_t *sem)
>   static void hash_sem_dec_count(sem_t *sem)
>   {
>   	unsigned int i = hash_sem_handle(sem);
> +
>   	if (i != HASH_FULL) {
> +		pthread_mutex_lock(&mutex_lock_count);
>   		sem_hash_table[i].sem = sem;
>   		sem_hash_table[i].count--;
> +		pthread_mutex_unlock(&mutex_lock_count);
>   	}
>   }
>
> @@ -788,6 +801,8 @@ int fwts_acpica_init(fwts_framework *fw)
>   	if (fwts_acpica_init_called)
>   		return FWTS_ERROR;
>
> +	pthread_mutex_init(&mutex_lock_count, NULL);
> +
>   	fwts_acpica_fw = fw;
>
>   	AcpiDbgLevel = ACPI_NORMAL_DEFAULT;
> @@ -974,6 +989,7 @@ int fwts_acpica_deinit(void)
>   		return FWTS_ERROR;
>
>   	AcpiTerminate();
> +	pthread_mutex_destroy(&mutex_lock_count);
>
>   	FWTS_ACPICA_FREE(fwts_acpica_XSDT);
>   	FWTS_ACPICA_FREE(fwts_acpica_RSDT);
>
Acked-by: Alex Hung <alex.hung at canonical.com>