Revision: 494
http://www.exim.org/viewvc/pcre2?view=rev&revision=494
Author: ph10
Date: 2016-02-25 17:40:16 +0000 (Thu, 25 Feb 2016)
Log Message:
-----------
Correct information about multi-threaded compilation.
Modified Paths:
--------------
code/trunk/doc/pcre2api.3
Modified: code/trunk/doc/pcre2api.3
===================================================================
--- code/trunk/doc/pcre2api.3 2016-02-24 10:17:10 UTC (rev 493)
+++ code/trunk/doc/pcre2api.3 2016-02-25 17:40:16 UTC (rev 494)
@@ -1,4 +1,4 @@
-.TH PCRE2API 3 "06 February 2016" "PCRE2 10.22"
+.TH PCRE2API 3 "25 February 2016" "PCRE2 10.22"
.SH NAME
PCRE2 - Perl-compatible regular expressions (revised API)
.sp
@@ -488,15 +488,16 @@
.P
In a more complicated situation, where patterns are compiled only when they are
first needed, but are still shared between threads, pointers to compiled
-patterns must be protected from simultaneous access by multiple threads, at
+patterns must be protected from simultaneous writing by multiple threads, at
least until a pattern has been compiled. The logic can be something like this:
.sp
+ Get a read-only (shared) lock (mutex) for pointer
if (pointer == NULL)
{
- Get exclusive access to pointer
- if (pointer == NULL) pointer = pcre2_compile(...
- Release exclusive access to pointer
+ Get a write (unique) lock for pointer
+ pointer = pcre2_compile(...
}
+ Release the lock
Use pointer in pcre2_match()
.sp
Of course, testing for compilation errors should also be included in the code.
@@ -503,22 +504,9 @@
.P
If JIT is being used, but the JIT compilation is not being done immediately,
(perhaps waiting to see if the pattern is used often enough) similar logic is
-required. The PCRE2_INFO_JITSIZE information call can detect whether there has
-been a successful call to \fBpcre2_jit_compile()\fP, but there is no way to
-tell whether JIT has been called and failed (a very few pattern features are
-not supported by JIT). Therefore, a separate flag is needed:
-.sp
- if (!jit_tried)
- {
- Get exclusive access to jit_tried
- (if !jit_tried) pcre2_jit_compile(pointer, ...
- jit_tried = TRUE
- Release exclusive access to jit_tried
- }
- Use pointer in pcre2_match()
-.sp
-Other threads can use pointer for non-JIT matching while JIT compilation is in
-progress.
+required. JIT compilation updates a pointer within the compiled code block, so
+a thread must gain unique write access to the pointer before calling
+\fBpcre2_jit_compile()\fP.
.
.
.SS "Context blocks"
@@ -3221,6 +3209,6 @@
.rs
.sp
.nf
-Last updated: 06 February 2016
+Last updated: 25 February 2016
Copyright (c) 1997-2016 University of Cambridge.
.fi
