lkml.org 
[lkml]   [2012]   [Mar]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
SubjectRe: [RFC PATCH] checkpatch: Warn on use of yield()
From
Date
On Tue, 2012-03-06 at 09:41 -0800, Joe Perches wrote:
> Perhaps the kernel-doc comments in sched/core.c
> should/could be expanded/updated.

Something like this?

---
kernel/sched/core.c | 20 ++++++++++++++++++--
1 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 2963fbb..a05a0f7 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4577,8 +4577,24 @@ EXPORT_SYMBOL(__cond_resched_softirq);
/**
* yield - yield the current processor to other threads.
*
- * This is a shortcut for kernel-space yielding - it marks the
- * thread runnable and calls sys_sched_yield().
+ * Do not ever use this function, there's a 99% chance you're doing it wrong.
+ *
+ * The scheduler is at all times free to pick the calling task as the most
+ * eligible task to run, if removing the yield() call from your code breaks
+ * it, its already broken.
+ *
+ * Typical broken usage is:
+ *
+ * while (!event)
+ * yield();
+ *
+ * where one assumes that yield() will let 'the other' process run that will
+ * make event true. If the current task is a SCHED_FIFO task that will never
+ * happen. Never use yield() as a progress guarantee!!
+ *
+ * If you want to use yield() to wait for something, use wait_event().
+ * If you want to use yield() to be 'nice' for others, use cond_resched().
+ * If you still want to use yield(), do not!
*/
void __sched yield(void)
{


\
 
 \ /
  Last update: 2012-03-06 18:57    [W:0.069 / U:14.540 seconds]
©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site