Date: Mon, 4 Jan 1999 18:46:55 -0800 (PST) From: Marcia Perry (ITG staff) <mperry@george.lbl.gov> To: freebsd-questions@FreeBSD.ORG Subject: Pthreads Problems Message-ID: <199901050246.SAA21135@george.lbl.gov>
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Hi,
I'm writing an app in C++ using Pthreads. The code works nicely
under Solaris so I figure I must be doing something correctly!
However, under freeBSD, release 2.2.6, I'm experiencing the
following problems and would like your advice:
1). I declare global variables:
pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
and get these errors during the build:
"devserv.cc:69: `PTHREAD_MUTEX_INITIALIZER' was not declared in this scope
devserv.cc:70: `PTHREAD_COND_INITIALIZER' was not declared in this scope
"
My compile/link command line is:
CC -D_THREAD_SAFE -o devserv file1.cc file2.cc ... -lc_r
Yes, I double-checked that I am including <pthread.h>
According to Dave Butenhof's "Programming with POSIX Threads" book,
static initialization of mutexes and condition variables should be ok.
So why is freeBSD, rel. 2.2.6 forcing me into dynamic initialization?
Is my build command wrong or incomplete? Look like a problem with
my environment?
2). The app is a server that takes requests from remote clients and
communicates with serial devices (e.g., cameras) to carry out
these requests (e.g., pan or tilt a camera). So I have several
devices attached to my computer and I listen on several network
sockets for remote requests. I use threads to do blocked recvfrom()'s
on each socket, signal when a request is added to a list, and do
the typical stuff (e.g., main() gets the signal and processes
the request). No problems here. But this scenario forces me to
terminate only when user types a contrl character (cntl-C, e.g.)
or if I blow it and seg fault or bus error... So, in a single-
threaded version, I had a nice signal handler to catch SIGINT,
SIGSEGV, etc., and before exiting, turning off the cameras, one
at a time.
In the threaded version, I have been advised NOT to use a signal
handler. Rather, create a thread to wait for the signals in
a sigset_t variable (and call sigwait()). And mask out the
signals from all the other threads that you do NOT want to catch
them. Fine. So I copied D. Butenhof's source code (page 228)
from his book to see how this was done. It works great under
Solaris. Under freeBSD, at least for version 2.2.6, sigwait()
doesn't seem to work -- I never get the SIGINT and need to
terminate with the manual "ps" and "kill" commands.
Is this a bug under release 2.2.6?
3). I looked at pthread.h to see how pthread_t is defined and did
see it typedef'd as a pointer to a structure. But searching
through all the headers did not reveal the definition of that
pthread_t structure. And I couldn't find sigwait() in either
the man pages nor the headers. However, the following
showed the sigwait() function to be defined and located in
-lc_r --
mperry@zippy(87)>nm -p libc_r.so.3.0 | grep sigwait
libc_r.so.3.0:00000280 T _sigwait
Where then is sigwait() defined/documented?
Thanks for your time and help--
Marcia
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