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Message-ID: <20240216180559.208276-8-tj@kernel.org>
Date: Fri, 16 Feb 2024 08:04:48 -1000
From: Tejun Heo <tj@...nel.org>
To: jiangshanlai@...il.com
Cc: torvalds@...ux-foundation.org,
linux-kernel@...r.kernel.org,
allen.lkml@...il.com,
kernel-team@...a.com,
Tejun Heo <tj@...nel.org>
Subject: [PATCH 07/17] workqueue: Clean up enum work_bits and related constants
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@...nel.org>
---
include/linux/workqueue.h | 58 +++++++++++++++++++++------------------
kernel/workqueue.c | 8 +++---
2 files changed, 36 insertions(+), 30 deletions(-)
diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index 1565bab9edc8..0ad534fe6673 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -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,
+ WORK_STRUCT_PWQ_SHIFT = 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,
+ /*
+ * 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_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, 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.
+ * 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_FLAG_BITS = 1,
- WORK_OFFQ_POOL_SHIFT = WORK_OFFQ_FLAG_BASE + WORK_OFFQ_FLAG_BITS,
+ 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() \
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 317c85f051b0..7c6915e23c5c 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -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));
--
2.43.2
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