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workqueue: Clean up enum work_bits and related constants

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The bits of work->data are used for a few different purposes. How the bits
are used is determined by enum work_bits. The planned disable/enable support
will add another use, so let's clean it up a bit in preparation.

- Let WORK_STRUCT_*_BIT's values be determined by enum definition order.

- Deliminate different bit sections the same way using SHIFT and BITS
  values.

- Rename __WORK_OFFQ_CANCELING to WORK_OFFQ_CANCELING_BIT for consistency.

- Introduce WORK_STRUCT_PWQ_SHIFT and replace WORK_STRUCT_FLAG_MASK and
  WORK_STRUCT_WQ_DATA_MASK with WQ_STRUCT_PWQ_MASK for clarity.

- Improve documentation.

No functional changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
This commit is contained in:
Tejun Heo 2024-02-20 19:36:14 -10:00
parent c5f5b9422a
commit e9a8e01f9b
2 changed files with 37 additions and 31 deletions
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60
include/linux/workqueue.h
View File

@ -24,41 +24,49 @@
enum work_bits {
WORK_STRUCT_PENDING_BIT = 0, /* work item is pending execution */
WORK_STRUCT_INACTIVE_BIT= 1, /* work item is inactive */
WORK_STRUCT_PWQ_BIT = 2, /* data points to pwq */
WORK_STRUCT_LINKED_BIT = 3, /* next work is linked to this one */
WORK_STRUCT_INACTIVE_BIT, /* work item is inactive */
WORK_STRUCT_PWQ_BIT, /* data points to pwq */
WORK_STRUCT_LINKED_BIT, /* next work is linked to this one */
#ifdef CONFIG_DEBUG_OBJECTS_WORK
WORK_STRUCT_STATIC_BIT = 4, /* static initializer (debugobjects) */
WORK_STRUCT_COLOR_SHIFT = 5, /* color for workqueue flushing */
#else
WORK_STRUCT_COLOR_SHIFT = 4, /* color for workqueue flushing */
WORK_STRUCT_STATIC_BIT, /* static initializer (debugobjects) */
#endif
WORK_STRUCT_FLAG_BITS,
/* color for workqueue flushing */
WORK_STRUCT_COLOR_SHIFT = WORK_STRUCT_FLAG_BITS,
WORK_STRUCT_COLOR_BITS = 4,
/*
* Reserve 8 bits off of pwq pointer w/ debugobjects turned off.
* This makes pwqs aligned to 256 bytes and allows 16 workqueue
* flush colors.
* When WORK_STRUCT_PWQ is set, reserve 8 bits off of pwq pointer w/
* debugobjects turned off. This makes pwqs aligned to 256 bytes (512
* bytes w/ DEBUG_OBJECTS_WORK) and allows 16 workqueue flush colors.
*
* MSB
* [ pwq pointer ] [ flush color ] [ STRUCT flags ]
* 4 bits 4 or 5 bits
*/
WORK_STRUCT_FLAG_BITS = WORK_STRUCT_COLOR_SHIFT +
WORK_STRUCT_COLOR_BITS,
/* data contains off-queue information when !WORK_STRUCT_PWQ */
WORK_OFFQ_FLAG_BASE = WORK_STRUCT_COLOR_SHIFT,
__WORK_OFFQ_CANCELING = WORK_OFFQ_FLAG_BASE,
WORK_STRUCT_PWQ_SHIFT = WORK_STRUCT_COLOR_SHIFT + WORK_STRUCT_COLOR_BITS,
/*
* When a work item is off queue, its high bits point to the last
* pool it was on. Cap at 31 bits and use the highest number to
* indicate that no pool is associated.
* data contains off-queue information when !WORK_STRUCT_PWQ.
*
* MSB
* [ pool ID ] [ OFFQ flags ] [ STRUCT flags ]
* 1 bit 4 or 5 bits
*/
WORK_OFFQ_FLAG_BITS = 1,
WORK_OFFQ_POOL_SHIFT = WORK_OFFQ_FLAG_BASE + WORK_OFFQ_FLAG_BITS,
WORK_OFFQ_FLAG_SHIFT = WORK_STRUCT_FLAG_BITS,
WORK_OFFQ_CANCELING_BIT = WORK_OFFQ_FLAG_SHIFT,
WORK_OFFQ_FLAG_END,
WORK_OFFQ_FLAG_BITS = WORK_OFFQ_FLAG_END - WORK_OFFQ_FLAG_SHIFT,
/*
* When a work item is off queue, the high bits encode off-queue flags
* and the last pool it was on. Cap pool ID to 31 bits and use the
* highest number to indicate that no pool is associated.
*/
WORK_OFFQ_POOL_SHIFT = WORK_OFFQ_FLAG_SHIFT + WORK_OFFQ_FLAG_BITS,
WORK_OFFQ_LEFT = BITS_PER_LONG - WORK_OFFQ_POOL_SHIFT,
WORK_OFFQ_POOL_BITS = WORK_OFFQ_LEFT <= 31 ? WORK_OFFQ_LEFT : 31,
};
enum work_flags {
@ -88,12 +96,10 @@ enum wq_misc_consts {
};
/* Convenience constants - of type 'unsigned long', not 'enum'! */
#define WORK_OFFQ_CANCELING (1ul << __WORK_OFFQ_CANCELING)
#define WORK_OFFQ_CANCELING (1ul << WORK_OFFQ_CANCELING_BIT)
#define WORK_OFFQ_POOL_NONE ((1ul << WORK_OFFQ_POOL_BITS) - 1)
#define WORK_STRUCT_NO_POOL (WORK_OFFQ_POOL_NONE << WORK_OFFQ_POOL_SHIFT)
#define WORK_STRUCT_FLAG_MASK ((1ul << WORK_STRUCT_FLAG_BITS) - 1)
#define WORK_STRUCT_WQ_DATA_MASK (~WORK_STRUCT_FLAG_MASK)
#define WORK_STRUCT_PWQ_MASK (~((1ul << WORK_STRUCT_PWQ_SHIFT) - 1))
#define WORK_DATA_INIT() ATOMIC_LONG_INIT((unsigned long)WORK_STRUCT_NO_POOL)
#define WORK_DATA_STATIC_INIT() \

8
kernel/workqueue.c
View File

@ -247,7 +247,7 @@ enum pool_workqueue_stats {
};
/*
* The per-pool workqueue. While queued, the lower WORK_STRUCT_FLAG_BITS
* The per-pool workqueue. While queued, bits below WORK_PWQ_SHIFT
* of work_struct->data are used for flags and the remaining high bits
* point to the pwq; thus, pwqs need to be aligned at two's power of the
* number of flag bits.
@ -294,7 +294,7 @@ struct pool_workqueue {
*/
struct kthread_work release_work;
struct rcu_head rcu;
} __aligned(1 << WORK_STRUCT_FLAG_BITS);
} __aligned(1 << WORK_STRUCT_PWQ_SHIFT);
/*
* Structure used to wait for workqueue flush.
@ -843,7 +843,7 @@ static void clear_work_data(struct work_struct *work)
static inline struct pool_workqueue *work_struct_pwq(unsigned long data)
{
return (struct pool_workqueue *)(data & WORK_STRUCT_WQ_DATA_MASK);
return (struct pool_workqueue *)(data & WORK_STRUCT_PWQ_MASK);
}
static struct pool_workqueue *get_work_pwq(struct work_struct *work)
@ -4851,7 +4851,7 @@ static void pwq_release_workfn(struct kthread_work *work)
static void init_pwq(struct pool_workqueue *pwq, struct workqueue_struct *wq,
struct worker_pool *pool)
{
BUG_ON((unsigned long)pwq & WORK_STRUCT_FLAG_MASK);
BUG_ON((unsigned long)pwq & ~WORK_STRUCT_PWQ_MASK);
memset(pwq, 0, sizeof(*pwq));