From b5490077274482efde57a50b060b99bc839acd45 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Fri, 3 Aug 2012 10:30:46 -0700 Subject: [PATCH] workqueue: introduce WORK_OFFQ_FLAG_* Low WORK_STRUCT_FLAG_BITS bits of work_struct->data contain WORK_STRUCT_FLAG_* and flush color. If the work item is queued, the rest point to the cpu_workqueue with WORK_STRUCT_CWQ set; otherwise, WORK_STRUCT_CWQ is clear and the bits contain the last CPU number - either a real CPU number or one of WORK_CPU_*. Scheduled addition of mod_delayed_work[_on]() requires an additional flag, which is used only while a work item is off queue. There are more than enough bits to represent off-queue CPU number on both 32 and 64bits. This patch introduces WORK_OFFQ_FLAG_* which occupy the lower part of the @work->data high bits while off queue. This patch doesn't define any actual OFFQ flag yet. Off-queue CPU number is now shifted by WORK_OFFQ_CPU_SHIFT, which adds the number of bits used by OFFQ flags to WORK_STRUCT_FLAG_SHIFT, to make room for OFFQ flags. To avoid shift width warning with large WORK_OFFQ_FLAG_BITS, ulong cast is added to WORK_STRUCT_NO_CPU and, just in case, BUILD_BUG_ON() to check that there are enough bits to accomodate off-queue CPU number is added. This patch doesn't make any functional difference. Signed-off-by: Tejun Heo --- include/linux/workqueue.h | 8 +++++++- kernel/workqueue.c | 14 +++++++++----- 2 files changed, 16 insertions(+), 6 deletions(-) diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h index ab95fef38d56..f562674db404 100644 --- a/include/linux/workqueue.h +++ b/include/linux/workqueue.h @@ -68,9 +68,15 @@ enum { WORK_STRUCT_FLAG_BITS = WORK_STRUCT_COLOR_SHIFT + WORK_STRUCT_COLOR_BITS, + /* data contains off-queue information when !WORK_STRUCT_CWQ */ + WORK_OFFQ_FLAG_BASE = WORK_STRUCT_FLAG_BITS, + WORK_OFFQ_FLAG_BITS = 0, + WORK_OFFQ_CPU_SHIFT = WORK_OFFQ_FLAG_BASE + WORK_OFFQ_FLAG_BITS, + + /* convenience constants */ WORK_STRUCT_FLAG_MASK = (1UL << WORK_STRUCT_FLAG_BITS) - 1, WORK_STRUCT_WQ_DATA_MASK = ~WORK_STRUCT_FLAG_MASK, - WORK_STRUCT_NO_CPU = WORK_CPU_NONE << WORK_STRUCT_FLAG_BITS, + WORK_STRUCT_NO_CPU = (unsigned long)WORK_CPU_NONE << WORK_OFFQ_CPU_SHIFT, /* bit mask for work_busy() return values */ WORK_BUSY_PENDING = 1 << 0, diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 0f50f4078e36..eeae77079483 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -533,9 +533,9 @@ static int work_next_color(int color) } /* - * A work's data points to the cwq with WORK_STRUCT_CWQ set while the - * work is on queue. Once execution starts, WORK_STRUCT_CWQ is - * cleared and the work data contains the cpu number it was last on. + * While queued, %WORK_STRUCT_CWQ is set and non flag bits of a work's data + * contain the pointer to the queued cwq. Once execution starts, the flag + * is cleared and the high bits contain OFFQ flags and CPU number. * * set_work_cwq(), set_work_cpu_and_clear_pending() and clear_work_data() * can be used to set the cwq, cpu or clear work->data. These functions @@ -565,7 +565,7 @@ static void set_work_cwq(struct work_struct *work, static void set_work_cpu_and_clear_pending(struct work_struct *work, unsigned int cpu) { - set_work_data(work, cpu << WORK_STRUCT_FLAG_BITS, 0); + set_work_data(work, (unsigned long)cpu << WORK_OFFQ_CPU_SHIFT, 0); } static void clear_work_data(struct work_struct *work) @@ -592,7 +592,7 @@ static struct global_cwq *get_work_gcwq(struct work_struct *work) return ((struct cpu_workqueue_struct *) (data & WORK_STRUCT_WQ_DATA_MASK))->pool->gcwq; - cpu = data >> WORK_STRUCT_FLAG_BITS; + cpu = data >> WORK_OFFQ_CPU_SHIFT; if (cpu == WORK_CPU_NONE) return NULL; @@ -3724,6 +3724,10 @@ static int __init init_workqueues(void) unsigned int cpu; int i; + /* make sure we have enough bits for OFFQ CPU number */ + BUILD_BUG_ON((1LU << (BITS_PER_LONG - WORK_OFFQ_CPU_SHIFT)) < + WORK_CPU_LAST); + cpu_notifier(workqueue_cpu_up_callback, CPU_PRI_WORKQUEUE_UP); cpu_notifier(workqueue_cpu_down_callback, CPU_PRI_WORKQUEUE_DOWN); -- 2.39.5