diff options
author | Tejun Heo <tj@kernel.org> | 2010-07-22 14:14:25 +0200 |
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committer | Tejun Heo <tj@kernel.org> | 2010-07-22 22:39:22 +0200 |
commit | e120153ddf8620fd0a194d301e9c5a8b28483bb5 (patch) | |
tree | 953ef1a61ca29d0486a6c8c3bb72dd8bbc080419 /kernel | |
parent | f2e005aaff4878a8ea93d5fb033a21389b72579a (diff) | |
download | op-kernel-dev-e120153ddf8620fd0a194d301e9c5a8b28483bb5.zip op-kernel-dev-e120153ddf8620fd0a194d301e9c5a8b28483bb5.tar.gz |
workqueue: fix how cpu number is stored in work->data
Once a work starts execution, its data contains the cpu number it was
on instead of pointing to cwq. This is added by commit 7a22ad75
(workqueue: carry cpu number in work data once execution starts) to
reliably determine the work was last on even if the workqueue itself
was destroyed inbetween.
Whether data points to a cwq or contains a cpu number was
distinguished by comparing the value against PAGE_OFFSET. The
assumption was that a cpu number should be below PAGE_OFFSET while a
pointer to cwq should be above it. However, on architectures which
use separate address spaces for user and kernel spaces, this doesn't
hold as PAGE_OFFSET is zero.
Fix it by using an explicit flag, WORK_STRUCT_CWQ, to mark what the
data field contains. If the flag is set, it's pointing to a cwq;
otherwise, it contains a cpu number.
Reported on s390 and microblaze during linux-next testing.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Sachin Sant <sachinp@in.ibm.com>
Reported-by: Michal Simek <michal.simek@petalogix.com>
Reported-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Tested-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Tested-by: Michal Simek <monstr@monstr.eu>
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/workqueue.c | 36 |
1 files changed, 13 insertions, 23 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index c11edc9..e5cb7fa 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -468,10 +468,9 @@ static int work_next_color(int color) } /* - * Work data points to the cwq while a work is on queue. Once - * execution starts, it points to the cpu the work was last on. This - * can be distinguished by comparing the data value against - * PAGE_OFFSET. + * 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. * * set_work_{cwq|cpu}() and clear_work_data() can be used to set the * cwq, cpu or clear work->data. These functions should only be @@ -494,7 +493,7 @@ static void set_work_cwq(struct work_struct *work, unsigned long extra_flags) { set_work_data(work, (unsigned long)cwq, - WORK_STRUCT_PENDING | extra_flags); + WORK_STRUCT_PENDING | WORK_STRUCT_CWQ | extra_flags); } static void set_work_cpu(struct work_struct *work, unsigned int cpu) @@ -507,25 +506,24 @@ static void clear_work_data(struct work_struct *work) set_work_data(work, WORK_STRUCT_NO_CPU, 0); } -static inline unsigned long get_work_data(struct work_struct *work) -{ - return atomic_long_read(&work->data) & WORK_STRUCT_WQ_DATA_MASK; -} - static struct cpu_workqueue_struct *get_work_cwq(struct work_struct *work) { - unsigned long data = get_work_data(work); + unsigned long data = atomic_long_read(&work->data); - return data >= PAGE_OFFSET ? (void *)data : NULL; + if (data & WORK_STRUCT_CWQ) + return (void *)(data & WORK_STRUCT_WQ_DATA_MASK); + else + return NULL; } static struct global_cwq *get_work_gcwq(struct work_struct *work) { - unsigned long data = get_work_data(work); + unsigned long data = atomic_long_read(&work->data); unsigned int cpu; - if (data >= PAGE_OFFSET) - return ((struct cpu_workqueue_struct *)data)->gcwq; + if (data & WORK_STRUCT_CWQ) + return ((struct cpu_workqueue_struct *) + (data & WORK_STRUCT_WQ_DATA_MASK))->gcwq; cpu = data >> WORK_STRUCT_FLAG_BITS; if (cpu == WORK_CPU_NONE) @@ -3501,14 +3499,6 @@ void __init init_workqueues(void) unsigned int cpu; int i; - /* - * The pointer part of work->data is either pointing to the - * cwq or contains the cpu number the work ran last on. Make - * sure cpu number won't overflow into kernel pointer area so - * that they can be distinguished. - */ - BUILD_BUG_ON(WORK_CPU_LAST << WORK_STRUCT_FLAG_BITS >= PAGE_OFFSET); - hotcpu_notifier(workqueue_cpu_callback, CPU_PRI_WORKQUEUE); /* initialize gcwqs */ |