threads impacts summary
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In HP-UX 10.30 and later releases, HP-UX supports 1x1 kernel
threads. This enhancement has the following implications:
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changes to errno, h_errno, and getdate_err
- In traditional non-threaded applications on HP-UX, errno is a
global integer. This traditional errno behavior works correctly in
user space (DCE) multi-threaded applications because threads are managed in the
user space and
errno is a part of the context of an individual thread. In HP-UX
10.30 and later releases, thread management is done within the kernel and
therefore errno
has to be managed on a per-thread basis.
- The variables getdate_err and h_errno become
per-thread variables in a similar way. The names getdate_err and
h_errno also are unusable for structure element names for source
compiled with -D_REENTRANT that uses time.h.
- If a shared library libother.sl is rebuilt on 10.30 or later
to take advantage of the new per-thread errno feature, it may break
binary compatibility for applications linked against it on earlier releases.
Specifically, applications that linked with an archived libc and
shared libother on a prior release will be broken. (HP-UX does
not support such linkage.) Applications linked with shared libc
are not broken. The solution is that the per-thread errno feature
is relevant only to applications using 1x1 kernel threads. Compilation with
-D_REENTRANT is not required for libraries that are not used in
such applications. Application breakage can be prevented by versioning libother.1.
changes to libc
- libc routines now support threads. Most of the routines that
have been modified continue to work in a threaded application as they did
in non-threaded ones, requiring no changes on the part of a programmer porting
code to a threaded environment. But in some cases the interface had to be
changed, and in these cases HP-UX 10.x provides two versions of the routine
— the original version for non-threaded applications, and a new version
for threaded applications.
- A number of obsolete interfaces provided in libc for multi-threaded
applications development in earlier releases of HP-UX have been moved from
libc to a new library named libd4r. The corresponding interfaces
are now thread-safe.
new man page, thread_safety(5)
For HP-UX 11i Version 1.5 on IPF, and following releases, a new man
page, thread_safety(5), consolidates all thread-safety information
for system functions and APIs in libc and libpthread.
Note: To include only Thread impacts when running the
scansummary and scandetail tools, use the option:
+C TH
To exclude these impacts, use the option:
-C TH
For more information on filtering output in reports, see Filtering the Output.
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