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<TITLE>Stdout console clogging => 300ms blocked</TITLE>
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<P><FONT SIZE=2 FACE="Arial">System details:</FONT>
<BR><FONT SIZE=2 FACE="Arial">Freescale MPC8347@200MHz</FONT>
<BR><FONT SIZE=2 FACE="Arial">Kernel 2.6.18</FONT>
</P>
<P><FONT SIZE=2 FACE="Arial">Problem:</FONT>
<BR><FONT SIZE=2 FACE="Arial">When we log debug output via the serial console on a multithreaded application, the console throughput may get clogged and then we experience a >300ms deadlock.</FONT></P>
<P><FONT SIZE=2 FACE="Arial">Quick and dirty test program: threadtest.c:</FONT>
<BR><FONT SIZE=2 FACE="Arial">//-----------------------------------------------------------------------------------------------</FONT>
<BR><FONT SIZE=2 FACE="Arial">#include <pthread.h></FONT>
<BR><FONT SIZE=2 FACE="Arial">#include <stdio.h></FONT>
<BR><FONT SIZE=2 FACE="Arial">#include <sys/time.h></FONT>
</P>
<P><FONT SIZE=2 FACE="Arial">#define THREAD_DELAY 1000</FONT>
</P>
<P><FONT SIZE=2 FACE="Arial">void* thread_1(void* unused)</FONT>
<BR><FONT SIZE=2 FACE="Arial">{</FONT>
<BR> <FONT SIZE=2 FACE="Arial">while (1)</FONT>
<BR> <FONT SIZE=2 FACE="Arial">{</FONT>
<BR> <FONT SIZE=2 FACE="Arial">usleep(THREAD_DELAY);</FONT>
<BR> <FONT SIZE=2 FACE="Arial">fprintf(stdout," <----- thread 1\n");</FONT>
<BR> <FONT SIZE=2 FACE="Arial">}</FONT>
<BR> <FONT SIZE=2 FACE="Arial">return NULL;</FONT>
<BR><FONT SIZE=2 FACE="Arial">}</FONT>
</P>
<P><FONT SIZE=2 FACE="Arial">void* thread_2(void* unused)</FONT>
<BR><FONT SIZE=2 FACE="Arial">{</FONT>
<BR> <FONT SIZE=2 FACE="Arial">static long ts_old;</FONT>
<BR> <FONT SIZE=2 FACE="Arial">long ts;</FONT>
<BR> <FONT SIZE=2 FACE="Arial">struct timeval tv;</FONT>
</P>
<P> <FONT SIZE=2 FACE="Arial">while (1)</FONT>
<BR> <FONT SIZE=2 FACE="Arial">{</FONT>
<BR> <FONT SIZE=2 FACE="Arial">usleep(THREAD_DELAY);</FONT>
<BR> <FONT SIZE=2 FACE="Arial">fprintf(stdout," <----- thread 2\n");</FONT>
</P>
<P> <FONT SIZE=2 FACE="Arial">gettimeofday (&tv, NULL);</FONT>
<BR> <FONT SIZE=2 FACE="Arial">ts = (tv.tv_sec * 1000L) + (tv.tv_usec / 1000L);</FONT>
<BR> <FONT SIZE=2 FACE="Arial">if ((ts - ts_old) > 100)</FONT>
<BR> <FONT SIZE=2 FACE="Arial">{</FONT>
<BR> <FONT SIZE=2 FACE="Arial">fprintf(stdout, "!!!!!!!!!!! thread2 interval timeout = %d ms\n",(int)(ts - ts_old));</FONT>
<BR> <FONT SIZE=2 FACE="Arial">}</FONT>
<BR> <FONT SIZE=2 FACE="Arial">ts_old = ts;</FONT>
<BR> <FONT SIZE=2 FACE="Arial">}</FONT>
<BR> <FONT SIZE=2 FACE="Arial">return NULL; </FONT>
</P>
<P><FONT SIZE=2 FACE="Arial">}</FONT>
</P>
<BR>
<BR>
<P><FONT SIZE=2 FACE="Arial">int main()</FONT>
<BR><FONT SIZE=2 FACE="Arial">{</FONT>
<BR> <FONT SIZE=2 FACE="Arial">pthread_t pthread_id_1, pthread_id_2;</FONT>
<BR>
<BR> <FONT SIZE=2 FACE="Arial">pthread_create(&pthread_id_1,NULL,&thread_1,NULL);</FONT>
<BR> <FONT SIZE=2 FACE="Arial">pthread_create(&pthread_id_2,NULL,&thread_2,NULL);</FONT>
<BR> <FONT SIZE=2 FACE="Arial">while (1)</FONT>
<BR> <FONT SIZE=2 FACE="Arial">{</FONT>
<BR> <FONT SIZE=2 FACE="Arial">}</FONT>
<BR> <FONT SIZE=2 FACE="Arial">return 0;</FONT>
</P>
<P><FONT SIZE=2 FACE="Arial">}</FONT>
</P>
<P><FONT SIZE=2 FACE="Arial">//-----------------------------------------------------------------------------------------------</FONT>
</P>
<P><FONT SIZE=2 FACE="Courier New">Build command on our platform: </FONT>
<BR><FONT SIZE=2 FACE="Courier New">powerpc-linux-uclibc-gcc threadtest.c -lpthread -o threadtest</FONT>
<BR><FONT SIZE=2 FACE="Courier New">Execute: ./threadtest > /dev/console &</FONT>
</P>
<P><FONT SIZE=2 FACE="Courier New">Uboot settings for the serial console:</FONT>
<BR><FONT SIZE=2 FACE="Courier New">consoledev=ttyS0</FONT>
<BR><FONT SIZE=2 FACE="Courier New">baudrate=115200</FONT>
<BR><FONT SIZE=2 FACE="Courier New">stdin=serial</FONT>
<BR><FONT SIZE=2 FACE="Courier New">stdout=serial</FONT>
<BR><FONT SIZE=2 FACE="Courier New">stderr=serial</FONT>
<BR><FONT SIZE=2 FACE="Courier New">boot_go=setenv bootargs console=$consoledev,$baudrate $args_rtc $args_mtd $args_nfs $args_debug;bootm $addr_kernel $addr_root $addr_dtb</FONT></P>
<BR>
<P><FONT SIZE=2 FACE="Courier New">Expected output [snippet] on the console:</FONT>
<BR><FONT SIZE=2 FACE="Courier New">.... /\ ........</FONT>
<BR><FONT SIZE=2 FACE="Courier New"> <----- thread 1</FONT>
<BR><FONT SIZE=2 FACE="Courier New"> <----- thread 2</FONT>
<BR><FONT SIZE=2 FACE="Courier New"> <----- thread 1</FONT>
<BR><FONT SIZE=2 FACE="Courier New"> <----- thread 2</FONT>
<BR><FONT SIZE=2 FACE="Courier New"> <----- thread 1</FONT>
<BR><FONT SIZE=2 FACE="Courier New"> <----- thread 2</FONT>
<BR><FONT SIZE=2 FACE="Courier New"> <----- thread 1</FONT>
<BR><FONT SIZE=2 FACE="Courier New"> <----- thread 2</FONT>
<BR><FONT SIZE=2 FACE="Courier New"> <----- thread 1</FONT>
<BR><FONT SIZE=2 FACE="Courier New"> <----- thread 2</FONT>
<BR><FONT SIZE=2 FACE="Courier New"> <----- thread 1</FONT>
<BR><FONT SIZE=2 FACE="Courier New">.... /\ ........</FONT>
</P>
<P><FONT SIZE=2 FACE="Courier New">Real output on the console:</FONT>
</P>
<P><FONT SIZE=2 FACE="Courier New">.... /\ ........</FONT>
<BR><FONT SIZE=2 FACE="Courier New"> <----- thread 1</FONT>
<BR><FONT SIZE=2 FACE="Courier New"> <----- thread 2</FONT>
<BR><FONT SIZE=2 FACE="Courier New"> <----- thread 1</FONT>
<BR><FONT SIZE=2 FACE="Courier New"> <----- thread 2</FONT>
<BR><FONT SIZE=2 FACE="Courier New"> <----- thread 1</FONT>
<BR><FONT SIZE=2 FACE="Courier New"> <----- thread 2</FONT>
<BR><FONT SIZE=2 FACE="Courier New">!!!!!!!!!!! thread2 interval timeout = 335 ms</FONT>
<BR><FONT SIZE=2 FACE="Courier New"> <----- thread 1</FONT>
<BR><FONT SIZE=2 FACE="Courier New"> <----- thread 2</FONT>
<BR><FONT SIZE=2 FACE="Courier New"> <----- thread 1</FONT>
<BR><FONT SIZE=2 FACE="Courier New"> <----- thread 2</FONT>
<BR><FONT SIZE=2 FACE="Courier New"> <----- thread 1</FONT>
<BR><FONT SIZE=2 FACE="Courier New">.... /\ ........ </FONT>
</P>
<P><FONT SIZE=2 FACE="Courier New">This timeout shows up around every second and has always about the same value of 335 ms.</FONT>
<BR><FONT SIZE=2 FACE="Courier New">Can somebody reproduce this behaviour ( the console speed and/or thread interval may have to be tweaked to clog the serial output) ?</FONT></P>
<P><FONT SIZE=2 FACE="Courier New">Thank you in advance for your help.</FONT>
<BR><FONT SIZE=2 FACE="Courier New">Bernard</FONT>
</P>
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<BR>
<P><B><FONT SIZE=1 FACE="Verdana">-----------------------------------------------------------</FONT></B>
<BR><B><SPAN LANG="fr-be"><FONT SIZE=1 FACE="Verdana">Bernard Willaert<BR>
</FONT></SPAN></B><SPAN LANG="fr-be"></SPAN><SPAN LANG="en-us"><FONT COLOR="#808080" SIZE=1 FACE="Verdana">Software Development Engineer Modality OEM Solutions</FONT></SPAN>
<BR><SPAN LANG="fr-be"><FONT SIZE=1 FACE="Verdana">BARCO Medical Imaging Division<BR>
</FONT><FONT COLOR="#808080" SIZE=1 FACE="Verdana">President Kennedypark 35 - B-8500 KORTRIJK - BELGIUM<BR>
Tel. +32 56 233 439 Fax +32 56 233 457<BR>
</FONT></SPAN><A HREF="file://www.barco.com/medical"><SPAN LANG="fr-be"><U></U><U><FONT COLOR="#0000FF" SIZE=1 FACE="Verdana">www.barco.com/medical</FONT></U></SPAN></A><SPAN LANG="fr-be"><BR>
</SPAN><A HREF="mailto:bernard.willaert@barco.com"><SPAN LANG="fr-be"><U></U><U><FONT COLOR="#0000FF" SIZE=1 FACE="Verdana">mailto:bernard.willaert@barco.com</FONT></U></SPAN></A><SPAN LANG="fr-be"></SPAN>
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