Hi,
This following commit
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=fdf8cb0909b531f9ae8f9b9d7e4eb35ba3505f07
un-inlined a low-level rwsem function, but did not mark it as
__sched. The result is that it now shows up as thread wchan (which also
affects /proc/profile stats). The following simple patch fixes this by
properly marking rwsem_down_failed_common() as a __sched function.
Also in this patch, which is up for discussion, marks down_read() and
down_write() proper as __sched. For profiling, it is pretty much useless to
know that a semaphore is beig help - it is necessary to know _which_
one. By going up another frame on the stack, the information becomes much
more useful.
In summary, the below change to lib/rwsem.c should be applied; the
changes to kernel/rwsem.c could be applied if other kernel hackers agree
with my proposal that down_read()/down_write() in the profile is not
enough.
Cheers,
Livio
Signed-off-by: Livio Soares <[email protected]>
kernel/rwsem.c | 4 ++--
lib/rwsem.c | 2 +-
2 files changed, 3 insertions(+), 3 deletions(-)
--- linux-2.6.24-rc2.orig/lib/rwsem.c 2007-11-06 16:57:46.000000000 -0500
+++ linux-2.6.24-rc2/lib/rwsem.c 2007-12-05 20:03:43.000000000 -0500
@@ -146,7 +146,7 @@ __rwsem_do_wake(struct rw_semaphore *sem
/*
* wait for a lock to be granted
*/
-static struct rw_semaphore *
+static struct rw_semaphore __sched *
rwsem_down_failed_common(struct rw_semaphore *sem,
struct rwsem_waiter *waiter, signed long adjustment)
{
--- linux-2.6.24-rc2.orig/kernel/rwsem.c 2007-11-06 16:57:46.000000000 -0500
+++ linux-2.6.24-rc2/kernel/rwsem.c 2007-12-05 21:09:55.000000000 -0500
@@ -15,7 +15,7 @@
/*
* lock for reading
*/
-void down_read(struct rw_semaphore *sem)
+void __sched down_read(struct rw_semaphore *sem)
{
might_sleep();
rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_);
@@ -42,7 +42,7 @@ EXPORT_SYMBOL(down_read_trylock);
/*
* lock for writing
*/
-void down_write(struct rw_semaphore *sem)
+void __sched down_write(struct rw_semaphore *sem)
{
might_sleep();
rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_);
--
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