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Full Discussion: Truss output interpretation
Top Forums UNIX for Advanced & Expert Users Truss output interpretation Post 302921532 by ghostdog74 on Friday 17th of October 2014 11:54:27 PM
Old 10-18-2014
Quote:
Originally Posted by jim mcnamara
Code:
         o    If O_NDELAY or O_NONBLOCK is set, read() returns -1
              and sets errno to EAGAIN.

pollsys then waits until the file can be read. The only possible cause is described above. This is POSIX compliant semantics for the read call. pollsys is a Solaris-ism (a system call entry point) for poll() and select(), I believe. Don Cragun would know definitely.
hi, thanks for the help.
This pertains to a networking process rather than file i/o process. One of my networking application is trying to connect to a server, and this happens. Below is truss output of what happens prior to the wait..

Code:
8094:    0.6895 open("/etc/netconfig", O_RDONLY|O_LARGEFILE)    = 4
8094:    0.6896 time()                                          = 1413538243
8094:    0.6901 rctlsys(0, "process.max-file-descriptor", 0x00000000, 0x00428020, 0, 0) = 0
8094:    0.6902 read(4, 0x00421524, 1024)                       = 1024
8094:      # p r a g m a   i d e n t\t " @ ( # ) n e t c o n f i g\t 1 . 1
8094:      6\t 9 9 / 1 0 / 2 5   S M I "\n #\n #   T h e   " N e t w o r k
.....

8094:      / t i c o t s           s t r a d d r . s o\n
8094:    0.6904 read(4, 0x00421524, 1024)                       = 0
8094:    0.6905 lseek(4, 0, SEEK_SET)                           = 0
8094:    0.6905 read(4, 0x00421524, 1024)                       = 1024
8094:      # p r a g m a   i d e n t\t " @ ( # ) n e t c o n f i g\t 1 . 1
8094:      6\t 9 9 / 1 0 / 2 5   S M I "\n #\n #   T h e   " N e t w o r k
8094:        C o n f i g u r a t i o n "   F i l e .\n #\n #   E a c h   e
8094:      n t r y   i s   o f   t h e   f o r m :\n #\n #               <
8094:      n e t w o r k _ i d >   < s e m a n t i c s >   < f l a g s ......

8094:      / t i c o t s           s t r a d d r . s o\n
8094:    0.6907 read(4, 0x00421524, 1024)                       = 0
8094:    0.6908 close(4)                                        = 0
8094:    0.6909 open("/dev/udp", O_RDONLY)                      = 4
8094:    0.6910 ioctl(4, SIOCGLIFNUM, 0xFFFFFD7FFFDEDC90)       = 0
8094:    0.6911 close(4)                                        = 0
8094:    0.6911 brk(0x0043AAB0)                                 = 0
8094:    0.6912 brk(0x0043EAB0)                                 = 0
8094:    0.6915 so_socket(PF_INET, SOCK_STREAM, IPPROTO_IP, "", SOV_DEFAULT) = 4
8094:    0.6916 ioctl(4, FIONBIO, 0xFFFFFD7FFFDEDCB0)           = 0
8094:    0.6924 connect(4, 0xFFFFFD7FFFDEE310, 16, SOV_DEFAULT) = 0
8094:    0.6925 getsockname(4, 0xFFFFFD7FFFDEE340, 0xFFFFFD7FFFDEE114, SOV_DEFAULT) = 0
8094:    0.6927 ioctl(4, FIONBIO, 0xFFFFFD7FFFDEE10C)           = 0
8094:    0.6928 setsockopt(4, tcp, TCP_NODELAY, 0xFFFFFD7FFFDEE10C, 4, SOV_DEFAULT) = 0
8094:    0.7024 brk(0x0043EAB0)                                 = 0
8094:    0.7025 brk(0x00446AB0)                                 = 0
8094:    0.7027 time()                                          = 1413538243
8094:    0.7028 write(4, 0x0043BE90, 236)                       = 236
8094:      T S H  \0\0\0EC020101\0\0\0\0\0\0\0\0\0 "02\0\0 303\0\0 I D
8094:     \f %\0\0\0\0 2\0F67F\0\0\0\0 @06FFC99A ; 
8094:      L              D6\0 303 X X X X X X
8094:                                                             01\0\0\0
8094:      j\0\0\0\0FF\0FFFFFFFFFFFFFFFFFFFFFFFFFFFFFF\0\0\0\0\0\0\n\0\0\0
8094:     02\0\0\09E1F\0\001\0\0\001\0\0\0 M Q C C 0 7 0 5 0 0 0 3\0\0\0\0
8094:     \0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0
8094:     \0\0\0\0\0\0\0\0\0\0\0\0
8094:    0.7029 read(4, 0x0043BE90, 32766)                      Err#11 EAGAIN

Is there any network tcp parameters that I can fine tune with regards to EAGAIN errors? My guess is network is slow (may be due to intermediate firewalls/routers etc), hence not able to read in time? Not really sure how to go on from here. Wondering also if performing a traceroute would do any good. any tips on troubleshooting this kind of errors greatly appreciated.
thanks
 

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