1 files changed, 58 insertions, 25 deletions

diff --git a/arch/um/kernel/sigio_user.c b/arch/um/kernel/sigio_user.c
index 62e5cfdf2188..f7b18e157d35 100644
--- a/arch/um/kernel/sigio_user.c
+++ b/arch/um/kernel/sigio_user.c
@@ -337,70 +337,103 @@ int ignore_sigio_fd(int fd)
         return(err);
 }
 
-static int setup_initial_poll(int fd)
+static struct pollfd* setup_initial_poll(int fd)
 {
         struct pollfd *p;
 
-        p = um_kmalloc_atomic(sizeof(struct pollfd));
-        if(p == NULL){
+        p = um_kmalloc(sizeof(struct pollfd));
+        if (p == NULL) {
                 printk("setup_initial_poll : failed to allocate poll\n");
-                return(-1);
+                return NULL;
         }
         *p = ((struct pollfd) { .fd     = fd,
                                 .events         = POLLIN,
                                 .revents        = 0 });
-        current_poll = ((struct pollfds) { .poll        = p,
-                                           .used        = 1,
-                                           .size        = 1 });
-        return(0);
+        return p;
 }
 
 void write_sigio_workaround(void)
 {
         unsigned long stack;
+        struct pollfd *p;
         int err;
+        int l_write_sigio_fds[2];
+        int l_sigio_private[2];
+        int l_write_sigio_pid;
 
+        /* We call this *tons* of times - and most ones we must just fail. */
         sigio_lock();
-        if(write_sigio_pid != -1)
-                goto out;
+        l_write_sigio_pid = write_sigio_pid;
+        sigio_unlock();
 
-        err = os_pipe(write_sigio_fds, 1, 1);
+        if (l_write_sigio_pid != -1)
+                return;
+
+        err = os_pipe(l_write_sigio_fds, 1, 1);
         if(err < 0){
                 printk("write_sigio_workaround - os_pipe 1 failed, "
                        "err = %d\n", -err);
-                goto out;
+                return;
         }
-        err = os_pipe(sigio_private, 1, 1);
+        err = os_pipe(l_sigio_private, 1, 1);
         if(err < 0){
-                printk("write_sigio_workaround - os_pipe 2 failed, "
+                printk("write_sigio_workaround - os_pipe 1 failed, "
                        "err = %d\n", -err);
                 goto out_close1;
         }
-        if(setup_initial_poll(sigio_private[1]))
+
+        p = setup_initial_poll(l_sigio_private[1]);
+        if(!p)
                 goto out_close2;
 
-        write_sigio_pid = run_helper_thread(write_sigio_thread, NULL, 
+        sigio_lock();
+
+        /* Did we race? Don't try to optimize this, please, it's not so likely
+         * to happen, and no more than once at the boot. */
+        if(write_sigio_pid != -1)
+                goto out_unlock;
+
+        write_sigio_pid = run_helper_thread(write_sigio_thread, NULL,
                                             CLONE_FILES | CLONE_VM, &stack, 0);
 
-        if(write_sigio_pid < 0) goto out_close2;
+        if (write_sigio_pid < 0)
+                goto out_clear;
 
-        if(write_sigio_irq(write_sigio_fds[0])) 
+        if (write_sigio_irq(l_write_sigio_fds[0]))
                 goto out_kill;
 
- out:
+        /* Success, finally. */
+        memcpy(write_sigio_fds, l_write_sigio_fds, sizeof(l_write_sigio_fds));
+        memcpy(sigio_private, l_sigio_private, sizeof(l_sigio_private));
+
+        current_poll = ((struct pollfds) { .poll        = p,
+                                           .used        = 1,
+                                           .size        = 1 });
+
         sigio_unlock();
         return;
 
  out_kill:
-        os_kill_process(write_sigio_pid, 1);
+        l_write_sigio_pid = write_sigio_pid;
         write_sigio_pid = -1;
+        sigio_unlock();
+        /* Going to call waitpid, avoid holding the lock. */
+        os_kill_process(l_write_sigio_pid, 1);
+        goto out_free;
+
+ out_clear:
+        write_sigio_pid = -1;
+ out_unlock:
+        sigio_unlock();
+ out_free:
+        kfree(p);
  out_close2:
-        os_close_file(sigio_private[0]);
-        os_close_file(sigio_private[1]);
+        os_close_file(l_sigio_private[0]);
+        os_close_file(l_sigio_private[1]);
  out_close1:
-        os_close_file(write_sigio_fds[0]);
-        os_close_file(write_sigio_fds[1]);
-        sigio_unlock();
+        os_close_file(l_write_sigio_fds[0]);
+        os_close_file(l_write_sigio_fds[1]);
+        return;
 }
 
 int read_sigio_fd(int fd)