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author | patacongo <patacongo@42af7a65-404d-4744-a932-0658087f49c3> | 2009-11-06 13:42:49 +0000 |
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committer | patacongo <patacongo@42af7a65-404d-4744-a932-0658087f49c3> | 2009-11-06 13:42:49 +0000 |
commit | 13712e46ce30b5ad84a30994d03fedfbab2a3820 (patch) | |
tree | 6dcb70dd4e2f0252df93897ac2bbe9f5d7aa9296 /nuttx/sched | |
parent | 3cd0ce8e626ad57b2695899278c62c057bab05ef (diff) | |
download | px4-nuttx-13712e46ce30b5ad84a30994d03fedfbab2a3820.tar.gz px4-nuttx-13712e46ce30b5ad84a30994d03fedfbab2a3820.tar.bz2 px4-nuttx-13712e46ce30b5ad84a30994d03fedfbab2a3820.zip |
Fix a potential race condition
git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@2234 42af7a65-404d-4744-a932-0658087f49c3
Diffstat (limited to 'nuttx/sched')
-rwxr-xr-x | nuttx/sched/work_cancel.c | 4 | ||||
-rwxr-xr-x | nuttx/sched/work_queue.c | 7 | ||||
-rwxr-xr-x | nuttx/sched/work_thread.c | 57 |
3 files changed, 43 insertions, 25 deletions
diff --git a/nuttx/sched/work_cancel.c b/nuttx/sched/work_cancel.c index d3a79f0b6..92393dec3 100755 --- a/nuttx/sched/work_cancel.c +++ b/nuttx/sched/work_cancel.c @@ -79,7 +79,9 @@ * Name: work_cancel * * Description: - * Cancel previously queued work. + * Cancel previously queued work. This removes work from the work queue. + * After work has been canceled, it may be re-queue by calling work_queue() + * again. * * Input parameters: * work - The previously queue work structure to cancel diff --git a/nuttx/sched/work_queue.c b/nuttx/sched/work_queue.c index 46afdc1d8..144c32178 100755 --- a/nuttx/sched/work_queue.c +++ b/nuttx/sched/work_queue.c @@ -83,6 +83,13 @@ * Queue work to be performed at a later time. All queued work will be * performed on the worker thread of of execution (not the caller's). * + * The work structure is allocated by caller, but completely managed by + * the work queue logic. The caller should never modify the contents of + * the work queue structure; the caller should not call work_queue() + * again until either (1) the previous work has been performed and removed + * from the queue, or (2) work_cancel() has been called to cancel the work + * and remove it from the work queue. + * * Input parameters: * work - The work structure to queue * worker - The worker callback to be invoked. The callback will invoked diff --git a/nuttx/sched/work_thread.c b/nuttx/sched/work_thread.c index 35a7f55ca..d1f415d77 100755 --- a/nuttx/sched/work_thread.c +++ b/nuttx/sched/work_thread.c @@ -101,6 +101,8 @@ struct dq_queue_s g_work; int work_thread(int argc, char *argv[]) { volatile FAR struct work_s *work; + worker_t worker; + FAR void *arg; irqstate_t flags; /* Loop forever */ @@ -130,37 +132,44 @@ int work_thread(int argc, char *argv[]) work = (FAR struct work_s *)g_work.head; while (work) { - /* Is this work ready? It is ready if there is no delay or if - * the delay has elapsed. - */ + /* Is this work ready? It is ready if there is no delay or if + * the delay has elapsed. + */ - if (work->delay == 0 || g_system_timer - work->qtime > work->delay) - { - /* Remove the ready-to-execute work from the list */ + if (work->delay == 0 || g_system_timer - work->qtime > work->delay) + { + /* Remove the ready-to-execute work from the list */ - (void)dq_rem((struct dq_entry_s *)work, &g_work); + (void)dq_rem((struct dq_entry_s *)work, &g_work); - /* Do the work. Re-enable interrupts while the work is being - * performed... we don't have any idea how long that will take! - */ + /* Extract the work description from the entry (in case the work + * instance by the re-used after it has been de-queued). + */ - irqrestore(flags); - work->worker(work->arg); + worker = work->worker; + arg = work->arg; - /* Now, unfortunately, since we re-enabled interrupts we don't - * the state of the work list and we will have to start back at - * the head of the list. - */ + /* Do the work. Re-enable interrupts while the work is being + * performed... we don't have any idea how long that will take! + */ - flags = irqsave(); - work = (FAR struct work_s *)g_work.head; - } - else - { - /* This one is not ready, try the next in the list. */ + irqrestore(flags); + worker(arg); - work = (FAR struct work_s *)work->dq.flink; - } + /* Now, unfortunately, since we re-enabled interrupts we don't + * know the state of the work list and we will have to start + * back at the head of the list. + */ + + flags = irqsave(); + work = (FAR struct work_s *)g_work.head; + } + else + { + /* This one is not ready, try the next in the list. */ + + work = (FAR struct work_s *)work->dq.flink; + } } irqrestore(flags); } |