avoid using pthread cleanup push/pop in stdio when not needed

unfortunately in dynamic-linked programs, these macros cause
pthread_self to be initialized, which costs a couple syscalls, and
(much worse) would necessarily fail, crash, and burn on ancient (2.4
and earlier) kernels where setting up a thread pointer does not work.

i'd like to do this in a more generic way that avoids all use of
cleanup push/pop before pthread_self has been successfully called and
avoids ugly if/else constructs like the one in this commit, but for
now, this will suffice.

diff --git a/src/stdio/__stdio_read.c b/src/stdio/__stdio_read.c
index ee17a57..c99ca9a 100644 (file)
--- a/src/stdio/__stdio_read.c
+++ b/src/stdio/__stdio_read.c
@@ -15,9 +15,13 @@ size_t __stdio_read(FILE *f, unsigned char *buf, size_t len)
        };
        ssize_t cnt;
 
-       pthread_cleanup_push(cleanup, f);
-       cnt = syscall_cp(SYS_readv, f->fd, iov, 2);
-       pthread_cleanup_pop(0);
+       if (libc.main_thread) {
+               pthread_cleanup_push(cleanup, f);
+               cnt = syscall_cp(SYS_readv, f->fd, iov, 2);
+               pthread_cleanup_pop(0);
+       } else {
+               cnt = syscall(SYS_readv, f->fd, iov, 2);
+       }
        if (cnt <= 0) {
                f->flags |= F_EOF ^ ((F_ERR^F_EOF) & cnt);
                f->rpos = f->rend = 0;

diff --git a/src/stdio/__stdio_write.c b/src/stdio/__stdio_write.c
index da45673..cef7bbd 100644 (file)
--- a/src/stdio/__stdio_write.c
+++ b/src/stdio/__stdio_write.c
@@ -18,9 +18,13 @@ size_t __stdio_write(FILE *f, const unsigned char *buf, size_t len)
        int iovcnt = 2;
        ssize_t cnt;
        for (;;) {
-               pthread_cleanup_push(cleanup, f);
-               cnt = syscall_cp(SYS_writev, f->fd, iov, iovcnt);
-               pthread_cleanup_pop(0);
+               if (libc.main_thread) {
+                       pthread_cleanup_push(cleanup, f);
+                       cnt = syscall_cp(SYS_writev, f->fd, iov, iovcnt);
+                       pthread_cleanup_pop(0);
+               } else {
+                       cnt = syscall(SYS_writev, f->fd, iov, iovcnt);
+               }
                if (cnt == rem) {
                        f->wend = f->buf + f->buf_size;
                        f->wpos = f->wbase = f->buf;