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diff --git a/xpa/man/man3/xparace.3 b/xpa/man/man3/xparace.3 deleted file mode 100644 index 6100196..0000000 --- a/xpa/man/man3/xparace.3 +++ /dev/null @@ -1,191 +0,0 @@ -.\" Automatically generated by Pod::Man 2.22 (Pod::Simple 3.13) -.\" -.\" Standard preamble: -.\" ======================================================================== -.de Sp \" Vertical space (when we can't use .PP) -.if t .sp .5v -.if n .sp -.. -.de Vb \" Begin verbatim text -.ft CW -.nf -.ne \\$1 -.. -.de Ve \" End verbatim text -.ft R -.fi -.. -.\" Set up some character translations and predefined strings. \*(-- will -.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left -.\" double quote, and \*(R" will give a right double quote. \*(C+ will -.\" give a nicer C++. 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No user-serviceable parts. -. \" fudge factors for nroff and troff -.if n \{\ -. ds #H 0 -. ds #V .8m -. ds #F .3m -. ds #[ \f1 -. ds #] \fP -.\} -.if t \{\ -. ds #H ((1u-(\\\\n(.fu%2u))*.13m) -. ds #V .6m -. ds #F 0 -. ds #[ \& -. ds #] \& -.\} -. \" simple accents for nroff and troff -.if n \{\ -. ds ' \& -. ds ` \& -. ds ^ \& -. ds , \& -. ds ~ ~ -. ds / -.\} -.if t \{\ -. ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u" -. ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u' -. ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u' -. ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u' -. ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u' -. ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u' -.\} -. \" troff and (daisy-wheel) nroff accents -.ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V' -.ds 8 \h'\*(#H'\(*b\h'-\*(#H' -.ds o \\k:\h'-(\\n(.wu+\w'\(de'u-\*(#H)/2u'\v'-.3n'\*(#[\z\(de\v'.3n'\h'|\\n:u'\*(#] -.ds d- \h'\*(#H'\(pd\h'-\w'~'u'\v'-.25m'\f2\(hy\fP\v'.25m'\h'-\*(#H' -.ds D- D\\k:\h'-\w'D'u'\v'-.11m'\z\(hy\v'.11m'\h'|\\n:u' -.ds th \*(#[\v'.3m'\s+1I\s-1\v'-.3m'\h'-(\w'I'u*2/3)'\s-1o\s+1\*(#] -.ds Th \*(#[\s+2I\s-2\h'-\w'I'u*3/5'\v'-.3m'o\v'.3m'\*(#] -.ds ae a\h'-(\w'a'u*4/10)'e -.ds Ae A\h'-(\w'A'u*4/10)'E -. \" corrections for vroff -.if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u' -.if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u' -. \" for low resolution devices (crt and lpr) -.if \n(.H>23 .if \n(.V>19 \ -\{\ -. ds : e -. ds 8 ss -. ds o a -. ds d- d\h'-1'\(ga -. ds D- D\h'-1'\(hy -. ds th \o'bp' -. ds Th \o'LP' -. ds ae ae -. ds Ae AE -.\} -.rm #[ #] #H #V #F C -.\" ======================================================================== -.\" -.IX Title "xparace 3" -.TH xparace 3 "July 23, 2013" "version 2.1.15" "SAORD Documentation" -.\" For nroff, turn off justification. Always turn off hyphenation; it makes -.\" way too many mistakes in technical documents. -.if n .ad l -.nh -.SH "NAME" -\&\fB\s-1XPA\s0 Race Conditions\fR -.SH "SYNOPSIS" -.IX Header "SYNOPSIS" -Potential \s-1XPA\s0 race conditions and how to avoid them. -.SH "DESCRIPTION" -.IX Header "DESCRIPTION" -Currently, there is only one known circumstance in which \s-1XPA\s0 can get -(temporarily) deadlocked in a race condition: if two or more \s-1XPA\s0 -servers send messages to one another using an \s-1XPA\s0 client routine such -as \fIXPASet()\fR, they can deadlock while each waits for the other server -to respond. (This can happen if the servers call \fIXPAPoll()\fR with a -time limit, and send messages in between the polling call.) The -reason this happens is that both client routines send a string to the -other server to establish the handshake and then wait for the server -response. Since each client is waiting for a response, neither is able -to enter its event-handling loop and respond to the other's -request. This deadlock will continue until one of the timeout periods -expire, at which point an error condition will be triggered and the -timed-out server will return to its event loop. -.PP -Starting with version 2.1.6, this rare race condition can be -avoided by setting the \s-1XPA_IOCALLSXPA\s0 environment variable for servers -that will make client calls. Setting this variable causes all \s-1XPA\s0 -socket \s-1IO\s0 calls to process outstanding \s-1XPA\s0 requests whenever the -primary socket is not ready for \s-1IO\s0. This means that a server making a -client call will (recursively) process incoming server requests while -waiting for client completion. It also means that a server callback -routine can handle incoming \s-1XPA\s0 messages if it makes its own \s-1XPA\s0 call. -The semi-public routine oldvalue=XPAIOCallsXPA(newvalue) can be used -to turn this behavior off and on temporarily. Passing a 0 will turn -off \s-1IO\s0 processing, 1 will turn it back on. The old value is returned -by the call. -.PP -By default, the \s-1XPA_IOCALLSXPA\s0 option is turned off, because we judge -that the added code complication and overhead involved will not be -justified by the amount of its use. Moreover, processing \s-1XPA\s0 requests -within socket \s-1IO\s0 can lead to non-intuitive results, since incoming -server requests will not necessarily be processed to completion in the -order in which they are received. -.PP -Aside from setting \s-1XPA_IOCALLSXPA\s0, the simplest way to avoid this race -condition is to multi-process: when you want to send a client message, -simply start a separate process to call the client routine, so that -the server is not stopped. It probably is fastest and easiest to use -\&\fIfork()\fR and then have the child call the client routine and exit. But -you also can use either the \fIsystem()\fR or \fIpopen()\fR routine to start one -of the command line programs and do the same thing. Alternatively, you -can use \s-1XPA\s0's internal \fIlaunch()\fR routine instead of \fIsystem()\fR. Based on -\&\fIfork()\fR and \fIexec()\fR, this routine is more secure than \fIsystem()\fR because -it does not call /bin/sh. -.PP -Starting with version 2.1.5, you also can send an \fIXPAInfo()\fR message with -the mode string \*(L"ack=false\*(R". This will cause the client to send a message -to the server and then exit without waiting for any return message from -the server. This UDP-like behavior will avoid the server deadlock when -sending short XPAInfo messages. -.SH "SEE ALSO" -.IX Header "SEE ALSO" -See xpa(n) for a list of \s-1XPA\s0 help pages |