On Thu, 21 Jun 2001, Louis-Philippe Gagnon wrote:
> No reactions the first time, let's try again.
>
> I've encountered a problem in the interaction betwen signals, longjmp and
> pthreads; I'm hoping someone can help me make sense of it.
>
> I've been trying to implement a IsBadReadPtr-style function in FreeBSD by
> using signal handlers and longjmp/setjmp. It seemed to work as expected,
> until I started using the -pthread option to gcc (thus linking against
> libc_r). Now the function only works on the first call; subsequent calls
> hang on the segmentation fault.
>
> Here's an example of the kind of code that causes problems :
Try this patch (to -stable). Only the patch to uthread_sig.c is
needed for -current.
--
Dan Eischen
Index: libc/i386/gen/setjmp.S
===================================================================
RCS file: /opt/FreeBSD/cvs/src/lib/libc/i386/gen/setjmp.S,v
retrieving revision 1.17.2.1
diff -u -r1.17.2.1 setjmp.S
--- libc/i386/gen/setjmp.S 2000/05/16 20:43:21 1.17.2.1
+++ libc/i386/gen/setjmp.S 2001/06/26 21:07:23
@@ -61,11 +61,7 @@
pushl %eax /* (sigset_t*)oset */
pushl $0 /* (sigset_t*)set */
pushl $1 /* SIG_BLOCK */
-#ifdef _THREAD_SAFE
- call PIC_PLT(CNAME(_thread_sys_sigprocmask))
-#else
call PIC_PLT(CNAME(sigprocmask))
-#endif
addl $12,%esp
PIC_EPILOGUE
movl 4(%esp),%ecx
@@ -91,11 +87,7 @@
leal 28(%edx), %eax
pushl %eax /* (sigset_t*)set */
pushl $3 /* SIG_SETMASK */
-#ifdef _THREAD_SAFE
- call PIC_PLT(CNAME(_thread_sys_sigprocmask))
-#else
call PIC_PLT(CNAME(sigprocmask))
-#endif
addl $12,%esp
PIC_EPILOGUE
movl 4(%esp),%edx
Index: libc/i386/gen/sigsetjmp.S
===================================================================
RCS file: /opt/FreeBSD/cvs/src/lib/libc/i386/gen/sigsetjmp.S,v
retrieving revision 1.19.2.1
diff -u -r1.19.2.1 sigsetjmp.S
--- libc/i386/gen/sigsetjmp.S 2000/05/16 20:43:21 1.19.2.1
+++ libc/i386/gen/sigsetjmp.S 2001/06/26 21:04:34
@@ -70,11 +70,7 @@
pushl %eax /* (sigset_t*)oset */
pushl $0 /* (sigset_t*)set */
pushl $1 /* SIG_BLOCK */
-#ifdef _THREAD_SAFE
- call PIC_PLT(CNAME(_thread_sys_sigprocmask))
-#else
call PIC_PLT(CNAME(sigprocmask))
-#endif
addl $12,%esp
PIC_EPILOGUE
movl 4(%esp),%ecx
@@ -102,11 +98,7 @@
leal 28(%edx), %eax
pushl %eax /* (sigset_t*)set */
pushl $3 /* SIG_SETMASK */
-#ifdef _THREAD_SAFE
- call PIC_PLT(CNAME(_thread_sys_sigprocmask))
-#else
call PIC_PLT(CNAME(sigprocmask))
-#endif
addl $12,%esp
PIC_EPILOGUE
movl 4(%esp),%edx
Index: libc_r/uthread/uthread_sig.c
===================================================================
RCS file: /opt/FreeBSD/cvs/src/lib/libc_r/uthread/uthread_sig.c,v
retrieving revision 1.25.2.7
diff -u -r1.25.2.7 uthread_sig.c
--- libc_r/uthread/uthread_sig.c 2001/06/23 00:47:05 1.25.2.7
+++ libc_r/uthread/uthread_sig.c 2001/06/26 20:56:52
@@ -931,6 +931,12 @@
thread->curframe = NULL;
PTHREAD_ASSERT(psf != NULL, "Invalid signal frame in signal handler");
+ /*
+ * We came here from the kernel scheduler; clear the in scheduler
+ * flag.
+ */
+ _thread_kern_in_sched = 0;
+
/* Check the threads previous state: */
if (psf->saved_state.psd_state != PS_RUNNING) {
/*
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