The attached patch uses RCU to avoid the need to acquire tasklist_lock
in the single-threaded case of clock_gettime(). It still acquires
tasklist_lock when for a (potentially multithreaded) process. This change
allows realtime applications to frequently monitor CPU consumption of
individual tasks, as requested (and now deployed) by some off-list users.
This has been in Ingo Molnar's -rt patchset since late 2005 with no
problems reported, and tests successfully on 2.6.20-rc6, so I believe
that it is long-since ready for mainline adoption.
Signed-off-by: Paul E. McKenney <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
---
kernel/posix-cpu-timers.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
Index: linux/kernel/posix-cpu-timers.c
===================================================================
--- linux.orig/kernel/posix-cpu-timers.c
+++ linux/kernel/posix-cpu-timers.c
@@ -304,7 +304,7 @@ int posix_cpu_clock_get(const clockid_t
* should be able to see it.
*/
struct task_struct *p;
- read_lock(&tasklist_lock);
+ rcu_read_lock();
p = find_task_by_pid(pid);
if (p) {
if (CPUCLOCK_PERTHREAD(which_clock)) {
@@ -313,11 +313,13 @@ int posix_cpu_clock_get(const clockid_t
p, &rtn);
}
} else if (p->tgid == pid && p->signal) {
+ read_lock(&tasklist_lock);
error = cpu_clock_sample_group(which_clock,
p, &rtn);
+ read_unlock(&tasklist_lock);
}
}
- read_unlock(&tasklist_lock);
+ rcu_read_unlock();
}
if (error)
----- End forwarded message -----
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
