| Date | Thu, 19 Apr 2007 16:12:53 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] bluetooth rfcomm: Convert to kthread API. |
| |
On Thu, 19 Apr 2007 01:58:54 -0600 "Eric W. Biederman" <ebiederm@xmission.com> wrote:
> From: Eric W. Biederman <ebiederm@xmission.com> > > This patch starts krfcommd using kthread_run instead of a combination > of kernel_thread and daemonize making the code slightly simpler > and more maintainable.
gargh, the more I look at these things, the more I agree with Christoph.
> Cc: Marcel Holtmann <marcel@holtmann.org> > Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> > --- > net/bluetooth/rfcomm/core.c | 4 ++-- > 1 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/net/bluetooth/rfcomm/core.c b/net/bluetooth/rfcomm/core.c > index 34f993a..baaad49 100644 > --- a/net/bluetooth/rfcomm/core.c > +++ b/net/bluetooth/rfcomm/core.c > @@ -38,6 +38,7 @@ > #include <linux/net.h> > #include <linux/mutex.h> > #include <linux/freezer.h> > +#include <linux/kthread.h> > > #include <net/sock.h> > #include <asm/uaccess.h> > @@ -1938,7 +1939,6 @@ static int rfcomm_run(void *unused) > > atomic_inc(&running); > > - daemonize("krfcommd"); > set_user_nice(current, -10); > > BT_DBG(""); > @@ -2058,7 +2058,7 @@ static int __init rfcomm_init(void) > > hci_register_cb(&rfcomm_cb); > > - kernel_thread(rfcomm_run, NULL, CLONE_KERNEL); > + kthread_run(rfcomm_run, NULL, "krfcommd"); > > if (class_create_file(bt_class, &class_attr_rfcomm_dlc) < 0) > BT_ERR("Failed to create RFCOMM info file");
We should remove the file-wide `terminate' and `running' and switch the thread management over to kthread_run(), kthread_stop() and kthread_should_stop().
btw, this:
static void rfcomm_worker(void) { BT_DBG("");
while (!atomic_read(&terminate)) { try_to_freeze();
if (!test_bit(RFCOMM_SCHED_WAKEUP, &rfcomm_event)) { /* No pending events. Let's sleep. * Incoming connections and data will wake us up. */ set_current_state(TASK_INTERRUPTIBLE); schedule(); }
/* Process stuff */ clear_bit(RFCOMM_SCHED_WAKEUP, &rfcomm_event); rfcomm_process_sessions(); } set_current_state(TASK_RUNNING); return; }
appears to have the classic sleep/wakeup bug: if the wakeup happens after we tested RFCOMM_SCHED_WAKEUP we will miss it.
Easy fix:
From: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org> ---
net/bluetooth/rfcomm/core.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-)
diff -puN net/bluetooth/rfcomm/core.c~rfcomm_worker-fix-wakeup-race net/bluetooth/rfcomm/core.c --- a/net/bluetooth/rfcomm/core.c~rfcomm_worker-fix-wakeup-race +++ a/net/bluetooth/rfcomm/core.c @@ -1855,18 +1855,18 @@ static void rfcomm_worker(void) while (!atomic_read(&terminate)) { try_to_freeze(); + set_current_state(TASK_INTERRUPTIBLE); if (!test_bit(RFCOMM_SCHED_WAKEUP, &rfcomm_event)) { /* No pending events. Let's sleep. * Incoming connections and data will wake us up. */ - set_current_state(TASK_INTERRUPTIBLE); schedule(); } + set_current_state(TASK_RUNNING); /* Process stuff */ clear_bit(RFCOMM_SCHED_WAKEUP, &rfcomm_event); rfcomm_process_sessions(); } - set_current_state(TASK_RUNNING); return; } _
(I think it's safer and saner to always run rfcomm_process_sessions() while in state TASK_RUNNING, not maybe-in-state-TASK_INTERRUPTIBLE)
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