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Re: I have a problem with the priority of ecos
(this email failed to be delivered - because of html contents - I set
sourceware.org as text domain now (instead of sources.redhat.com) - (i
must say, i prefer html for tables ;-))
On 04/13/2011 02:36 AM, moktar_bouain wrote:
On 04/12/2011 05:02 PM, moktar_bouain wrote:
Hi Thomas,
I use bitmap scheduling with 31 level for priority(by default).
I tried with diag_printf() but the same thing.
better use cyg_thread_delay(1). (not with 0 delay, this does nothing;
also cyg_thread_yield only switches between 2 threads with the same
priority)
What else is configured in your system (what template did you build from)?
My guess is that there is another thread already at priority 10.
Indeed. Here my list of default eCos thread priorities:
Priorities go from 0 to CYGNUM_KERNEL_SCHED_PRIORITIES-1. By default,
CYGNUM_KERNEL_SCHED_PRIORITIES=32.
So by default priorities go from 0 to 31.
priority name default stack name
default size
CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_
INVERSION_PROTOCOL_DEFAULT_PRIORITY 0
_POSIX_THREAD_PRIORITY_SCHEDULING 1 _POSIX_THREAD_ATTR_STACKSIZE
1 posix unit
CYGPKG_NET_FAST_THREAD_PRIORITY 6
CYGPKG_NET_THREAD_PRIORITY 7
CYGPKG_NET_DHCP_THREAD_PRIORITY 8
CYGINT_NET_IPV6_ROUTING_THREAD_PRIORITY 8
CYGNUM_LIBC_MAIN_THREAD_PRIORITY 10
CYGNUM_LIBC_MAIN_DEFAULT_STACK_SIZE 8192
CYGPKG_NET_TFTPD_THREAD_PRIORITY 10
CYGPKG_NET_TFTPD_THREAD_STACK_SIZE 3948
CYGNUM_HAL_COMMON_INTERRUPTS_STACK_SIZE 4096
CYGNUM_HTTPD_THREAD_PRIORITY 16 CYGNUM_HTTPD_THREAD_STACK_SIZE
2048
common TTY thread 20
common SMI thread 28
CYGNUM_JFFS2_GC_THREAD_PRIORITY 30
idle thread 31
Your main function has automatically a thread associated with priority
10. So apparently the printf of threadB blocks somewhere, then the main
thread can run, and it fires again both threads, so the highest priority
threadB can run.
I still don't know why you think that the threads should yield to each
other after each printf().
indeed. It is an RTOS. If the priorities are not equal, the highest
priority thread keeps on running until it has nothing to do (that is not
the case, it keeps on printing), or until it has to wait for something
or when it is blocked by something.
I used eCos for Leon3 (architecture SPARC) with the simulator Tsim.
I created this simple program that uses 2 threads.
The problem if there a difference of 10 between two levels of priority, the
program it works(5 and 15 or 10 and 20). But if less than 10 it does not
work
?
What do yo mean with "it works": In the original example, with A-10 and
B-0, B kept on running; with A-1 and B-0, both alternated.
Indeed, if printf would not block anywhere, threadB should keep running
forever.
But if I would implement serial_write, because most processors have a
hardware serial peripheral with a 2 byte alternating transmit buffer, I
would fill up that transmit buffer, and then block-wait on an interrupt
that the first buffer is empty. With a relatively fast 38400 baud rate,
this takes 208333ns, so worth block-waiting for.
On the at91 platform I know well, you can choose between a polled or
interrupt transmit.
So eCos is correct: with 10-0 threadB keeps on running, with 1-0 it
alternates.
By the way, it is only necessary to call cyg_thread_resume once; I have
a bad feeling about calling it more than once, I don't know if the
suspend counter can become negative and what happens then.... Please
check the documentation, or send a separate mail to ecos-discuss.
There is no need for a main function (with automatically a thread):
initialize (with resume) all threads in void cyg_user_start(void).
By the way: this mail is for ecos-discuss, not for ecos-devel (but I
don't follow ecos-discuss so closely anymore, so you are lucky ;-)
Regards,
Jürgen
----------------------------------------------------------------------------------------------
original mail:
Hello ,
I have a problem with the priority of ecos.
I have the following configuration:
#include<cyg/kernel/kapi.h>
#include<stdio.h>
#include<math.h>
#include<stdlib.h>
cyg_thread thread_s[2];
char stack[2][4096];
cyg_handle_t simple_threadA, simple_threadB;
cyg_mutex_t cliblock;
void taska(cyg_addrword_t data)
{
printf("TASKA \n");
}
void taskb(cyg_addrword_t data)
{
printf("TASKB \n");
}
void cyg_user_start(void)
{
printf("Entering twothreads' cyg_user_start() function\n");
cyg_mutex_init(&cliblock);
cyg_thread_create(10, taska, (cyg_addrword_t) 0,"Thread A", (void *)
stack[0], 4096,&simple_threadA,&thread_s[0]);
cyg_thread_create(0, taskb, (cyg_addrword_t) 1,"Thread B", (void *)
stack[1], 4096,&simple_threadB,&thread_s[1]);
}
void main (cyg_addrword_t data)
{
for(;;)
{
cyg_thread_resume(simple_threadA);
cyg_thread_resume(simple_threadB);
}
}
when I execute this configuration:
TASKB
TASKB
TASKB
TASKB
TASKB
TASKB
TASKB
TASKB
TASKB
TASKB
TASKB
but when I changed the priority:
cyg_thread_create(1, taska, (cyg_addrword_t) 0,"Thread A", (void *)
stack[0], 4096,&simple_threadA,&thread_s[0]);
cyg_thread_create(0, taskb, (cyg_addrword_t) 1,"Thread B", (void *)
stack[1], 4096,&simple_threadB,&thread_s[1]);
I find this false result
TASKB
TASKA
TASKB
TASKA
TASKB
TASKA
TASKB
TASKA
TASKB
TASKA
TASKB
TASKA
TASKB
TASKA
TASKB
Any help??
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