Re: [Xenomai-core] xnselect_destroy fails to wake up waiters
Gilles Chanteperdrix wrote: Jan Kiszka wrote: Gilles Chanteperdrix wrote: Jan Kiszka wrote: Hi Gilles, I tend to think that xnselect_destroy should signal an event on the dying fd instead of just clearing the binding. The task blocking on select currently does not get a hint that the fd is dead and will block on select until some other event arrives. That's unfortunately not standard conforming. Ok. Got it, I was mixing xnselect_destroy and xnselector_destroy. Yes, right, something should be done. What is supposed to happen? Is it supposed to be signaled as an exceptional condition? It should be signaled so that the caller tries to read/write/whatever and then gets the information that the fd is down. Looks to me like you get a wakeup for nothing... From the spec: http://www.opengroup.org/onlinepubs/009695399/functions/select.html I do not see anything specified for the fds closure. A descriptor shall be considered ready for reading when a call to an input function with O_NONBLOCK clear would not block, whether or not the function would transfer data successfully. (The function might return data, an end-of-file indication, or an error other than one indicating that it is blocked, and in each of these cases the descriptor shall be considered ready for reading.) Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux ___ Xenomai-core mailing list Xenomai-core@gna.org https://mail.gna.org/listinfo/xenomai-core
Re: [Xenomai-core] xnselect_destroy fails to wake up waiters
Jan Kiszka wrote: Gilles Chanteperdrix wrote: Jan Kiszka wrote: Gilles Chanteperdrix wrote: Jan Kiszka wrote: Hi Gilles, I tend to think that xnselect_destroy should signal an event on the dying fd instead of just clearing the binding. The task blocking on select currently does not get a hint that the fd is dead and will block on select until some other event arrives. That's unfortunately not standard conforming. Ok. Got it, I was mixing xnselect_destroy and xnselector_destroy. Yes, right, something should be done. What is supposed to happen? Is it supposed to be signaled as an exceptional condition? It should be signaled so that the caller tries to read/write/whatever and then gets the information that the fd is down. Looks to me like you get a wakeup for nothing... From the spec: http://www.opengroup.org/onlinepubs/009695399/functions/select.html I do not see anything specified for the fds closure. A descriptor shall be considered ready for reading when a call to an input function with O_NONBLOCK clear would not block, whether or not the function would transfer data successfully. (The function might return data, an end-of-file indication, or an error other than one indicating that it is blocked, and in each of these cases the descriptor shall be considered ready for reading.) Ok. But I need to think a bit for a correct implementation. The naïve implementation would result in the closed fd being constantly signaled and select no longer blocking. -- Gilles. ___ Xenomai-core mailing list Xenomai-core@gna.org https://mail.gna.org/listinfo/xenomai-core
Re: [Xenomai-core] xnselect_destroy fails to wake up waiters
Jan Kiszka wrote:
Hi Gilles,
I tend to think that xnselect_destroy should signal an event on the
dying fd instead of just clearing the binding. The task blocking on
select currently does not get a hint that the fd is dead and will block
on select until some other event arrives. That's unfortunately not
standard conforming.
Could you test the following patch? The fd will be in the pending set
until the fd is reused, but that should be harmless as long as the fd is
not in the expected set.
diff --git a/ksrc/nucleus/select.c b/ksrc/nucleus/select.c
index fd56bfb..17c5e0b 100644
--- a/ksrc/nucleus/select.c
+++ b/ksrc/nucleus/select.c
@@ -131,7 +131,8 @@ int xnselect_bind(struct xnselect *select_block,
__FD_SET(index, selector-fds[type].pending);
if (xnselect_wakeup(selector))
xnpod_schedule();
- }
+ } else
+ __FD_CLR(index, selector-fds[type].pending);
return 0;
}
@@ -178,6 +179,7 @@ EXPORT_SYMBOL_GPL(__xnselect_signal);
void xnselect_destroy(struct xnselect *select_block)
{
xnholder_t *holder;
+ int resched;
spl_t s;
xnlock_get_irqsave(nklock, s);
@@ -190,11 +192,18 @@ void xnselect_destroy(struct xnselect *select_block)
__FD_CLR(binding-bit_index,
selector-fds[binding-type].expected);
- __FD_CLR(binding-bit_index,
-selector-fds[binding-type].pending);
+ if (!__FD_ISSET(binding-bit_index,
+ selector-fds[binding-type].pending)) {
+ __FD_SET(binding-bit_index,
+selector-fds[binding-type].pending);
+ if (xnselect_wakeup(selector))
+ resched = 1;
+ }
removeq(selector-bindings, binding-slink);
xnlock_put_irqrestore(nklock, s);
+ if (resched)
+ xnpod_schedule();
xnfree(binding);
xnlock_get_irqsave(nklock, s);
--
Gilles.
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Re: [Xenomai-core] xnselect_destroy fails to wake up waiters
Gilles Chanteperdrix wrote:
Jan Kiszka wrote:
Hi Gilles,
I tend to think that xnselect_destroy should signal an event on the
dying fd instead of just clearing the binding. The task blocking on
select currently does not get a hint that the fd is dead and will block
on select until some other event arrives. That's unfortunately not
standard conforming.
Could you test the following patch? The fd will be in the pending set
until the fd is reused, but that should be harmless as long as the fd is
not in the expected set.
diff --git a/ksrc/nucleus/select.c b/ksrc/nucleus/select.c
index fd56bfb..17c5e0b 100644
--- a/ksrc/nucleus/select.c
+++ b/ksrc/nucleus/select.c
@@ -131,7 +131,8 @@ int xnselect_bind(struct xnselect *select_block,
__FD_SET(index, selector-fds[type].pending);
if (xnselect_wakeup(selector))
xnpod_schedule();
- }
+ } else
+ __FD_CLR(index, selector-fds[type].pending);
return 0;
}
@@ -178,6 +179,7 @@ EXPORT_SYMBOL_GPL(__xnselect_signal);
void xnselect_destroy(struct xnselect *select_block)
{
xnholder_t *holder;
+ int resched;
spl_t s;
xnlock_get_irqsave(nklock, s);
@@ -190,11 +192,18 @@ void xnselect_destroy(struct xnselect *select_block)
__FD_CLR(binding-bit_index,
selector-fds[binding-type].expected);
- __FD_CLR(binding-bit_index,
- selector-fds[binding-type].pending);
+ if (!__FD_ISSET(binding-bit_index,
+ selector-fds[binding-type].pending)) {
+ __FD_SET(binding-bit_index,
+ selector-fds[binding-type].pending);
+ if (xnselect_wakeup(selector))
+ resched = 1;
+ }
removeq(selector-bindings, binding-slink);
xnlock_put_irqrestore(nklock, s);
+ if (resched)
+ xnpod_schedule();
xnfree(binding);
xnlock_get_irqsave(nklock, s);
Works perfectly! You may test yourself using the RT-TCP examples from
latest RTnet git. :)
Thanks,
Jan
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Re: [Xenomai-core] xnselect_destroy fails to wake up waiters
Jan Kiszka wrote:
Gilles Chanteperdrix wrote:
Jan Kiszka wrote:
Hi Gilles,
I tend to think that xnselect_destroy should signal an event on the
dying fd instead of just clearing the binding. The task blocking on
select currently does not get a hint that the fd is dead and will block
on select until some other event arrives. That's unfortunately not
standard conforming.
Could you test the following patch? The fd will be in the pending set
until the fd is reused, but that should be harmless as long as the fd is
not in the expected set.
diff --git a/ksrc/nucleus/select.c b/ksrc/nucleus/select.c
index fd56bfb..17c5e0b 100644
--- a/ksrc/nucleus/select.c
+++ b/ksrc/nucleus/select.c
@@ -131,7 +131,8 @@ int xnselect_bind(struct xnselect *select_block,
__FD_SET(index, selector-fds[type].pending);
if (xnselect_wakeup(selector))
xnpod_schedule();
-}
+} else
+__FD_CLR(index, selector-fds[type].pending);
return 0;
}
@@ -178,6 +179,7 @@ EXPORT_SYMBOL_GPL(__xnselect_signal);
void xnselect_destroy(struct xnselect *select_block)
{
xnholder_t *holder;
+int resched;
spl_t s;
xnlock_get_irqsave(nklock, s);
@@ -190,11 +192,18 @@ void xnselect_destroy(struct xnselect *select_block)
__FD_CLR(binding-bit_index,
selector-fds[binding-type].expected);
-__FD_CLR(binding-bit_index,
- selector-fds[binding-type].pending);
+if (!__FD_ISSET(binding-bit_index,
+selector-fds[binding-type].pending)) {
+__FD_SET(binding-bit_index,
+ selector-fds[binding-type].pending);
+if (xnselect_wakeup(selector))
+resched = 1;
+}
removeq(selector-bindings, binding-slink);
xnlock_put_irqrestore(nklock, s);
+if (resched)
+xnpod_schedule();
xnfree(binding);
xnlock_get_irqsave(nklock, s);
Works perfectly! You may test yourself using the RT-TCP examples from
latest RTnet git. :)
Ok. Merged. It would need some work, as my test targets are all running
nfs. But that is certainly possible, as I think rtnetproxy now supports
UDP, does it?
--
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Re: [Xenomai-core] xnselect_destroy fails to wake up waiters
Gilles Chanteperdrix wrote:
Jan Kiszka wrote:
Gilles Chanteperdrix wrote:
Jan Kiszka wrote:
Hi Gilles,
I tend to think that xnselect_destroy should signal an event on the
dying fd instead of just clearing the binding. The task blocking on
select currently does not get a hint that the fd is dead and will block
on select until some other event arrives. That's unfortunately not
standard conforming.
Could you test the following patch? The fd will be in the pending set
until the fd is reused, but that should be harmless as long as the fd is
not in the expected set.
diff --git a/ksrc/nucleus/select.c b/ksrc/nucleus/select.c
index fd56bfb..17c5e0b 100644
--- a/ksrc/nucleus/select.c
+++ b/ksrc/nucleus/select.c
@@ -131,7 +131,8 @@ int xnselect_bind(struct xnselect *select_block,
__FD_SET(index, selector-fds[type].pending);
if (xnselect_wakeup(selector))
xnpod_schedule();
- }
+ } else
+ __FD_CLR(index, selector-fds[type].pending);
return 0;
}
@@ -178,6 +179,7 @@ EXPORT_SYMBOL_GPL(__xnselect_signal);
void xnselect_destroy(struct xnselect *select_block)
{
xnholder_t *holder;
+ int resched;
spl_t s;
xnlock_get_irqsave(nklock, s);
@@ -190,11 +192,18 @@ void xnselect_destroy(struct xnselect *select_block)
__FD_CLR(binding-bit_index,
selector-fds[binding-type].expected);
- __FD_CLR(binding-bit_index,
-selector-fds[binding-type].pending);
+ if (!__FD_ISSET(binding-bit_index,
+ selector-fds[binding-type].pending)) {
+ __FD_SET(binding-bit_index,
+selector-fds[binding-type].pending);
+ if (xnselect_wakeup(selector))
+ resched = 1;
+ }
removeq(selector-bindings, binding-slink);
xnlock_put_irqrestore(nklock, s);
+ if (resched)
+ xnpod_schedule();
xnfree(binding);
xnlock_get_irqsave(nklock, s);
Works perfectly! You may test yourself using the RT-TCP examples from
latest RTnet git. :)
Ok. Merged. It would need some work, as my test targets are all running
nfs. But that is certainly possible, as I think rtnetproxy now supports
UDP, does it?
Yep, should work, Wolfgang added it for the manroland scenario.
Jan
--
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Corporate Competence Center Embedded Linux
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