work around "signal loses thread pointer" issue with "approach 2"

this was discussed on the mailing list and no consensus on the
preferred solution was reached, so in anticipation of a release, i'm
just committing a minimally-invasive solution that avoids the problem
by ensuring that multi-threaded-capable programs will always have
initialized the thread pointer before any signal handler can run.

in the long term we may switch to initializing the thread pointer at
program start time whenever the program has the potential to access
any per-thread data.

diff --git a/src/signal/sigaction.c b/src/signal/sigaction.c
index 18956c6b24a84724143df86e1679fcc52a683620..5bc9383b66f34ed6f57e6d1f6a56bc57b8a8dc3c 100644 (file)
--- a/src/signal/sigaction.c
+++ b/src/signal/sigaction.c
@@ -3,9 +3,13 @@
 #include <errno.h>
 #include "syscall.h"
 #include "pthread_impl.h"
+#include "libc.h"
 
 void __restore(), __restore_rt();
 
+static pthread_t dummy(void) { return 0; }
+weak_alias(dummy, __pthread_self_def);
+
 int __libc_sigaction(int sig, const struct sigaction *sa, struct sigaction *old)
 {
        struct {
@@ -23,6 +27,7 @@ int __libc_sigaction(int sig, const struct sigaction *sa, struct sigaction *old)
                pksa = (long)&ksa;
        }
        if (old) pkold = (long)&kold;
+       __pthread_self_def();
        if (syscall(SYS_rt_sigaction, sig, pksa, pkold, 8))
                return -1;
        if (old) {

diff --git a/src/thread/pthread_self.c b/src/thread/pthread_self.c
index cc2ddfb72ff4cdb8e4bd5046c7326204f8dacd0e..51f12bb3227951668c7e75273e9d868a58ca63f2 100644 (file)
--- a/src/thread/pthread_self.c
+++ b/src/thread/pthread_self.c
@@ -19,7 +19,7 @@ static int init_main_thread()
        return 0;
 }
 
-pthread_t pthread_self()
+pthread_t __pthread_self_def()
 {
        static int init, failed;
        if (!init) {
@@ -31,4 +31,5 @@ pthread_t pthread_self()
        return __pthread_self();
 }
 
-weak_alias(pthread_self, __pthread_self_init);
+weak_alias(__pthread_self_def, pthread_self);
+weak_alias(__pthread_self_def, __pthread_self_init);