2 files changed, 10 insertions, 2 deletions

diff --git a/arch/um/kernel/skas/process_kern.c b/arch/um/kernel/skas/process_kern.c
index 3f70a2e12f06..14360ac17f02 100644
--- a/arch/um/kernel/skas/process_kern.c
+++ b/arch/um/kernel/skas/process_kern.c
@@ -35,6 +35,8 @@ void switch_to_skas(void *prev, void *next)
         switch_threads(&from->thread.mode.skas.switch_buf,
                        to->thread.mode.skas.switch_buf);
 
+        arch_switch_to_skas(current->thread.prev_sched, current);
+
         if(current->pid == 0)
                 switch_timers(1);
 }
diff --git a/arch/um/kernel/tt/process_kern.c b/arch/um/kernel/tt/process_kern.c
index 295c1ac817b3..a9c1443fc548 100644
--- a/arch/um/kernel/tt/process_kern.c
+++ b/arch/um/kernel/tt/process_kern.c
@@ -51,6 +51,13 @@ void switch_to_tt(void *prev, void *next)
 
         c = 0;
 
+        /* Notice that here we "up" the semaphore on which "to" is waiting, and
+         * below (the read) we wait on this semaphore (which is implemented by
+         * switch_pipe) and go sleeping. Thus, after that, we have resumed in
+         * "to", and can't use any more the value of "from" (which is outdated),
+         * nor the value in "to" (since it was the task which stole us the CPU,
+         * which we don't care about). */
+
         err = os_write_file(to->thread.mode.tt.switch_pipe[1], &c, sizeof(c));
         if(err != sizeof(c))
                 panic("write of switch_pipe failed, err = %d", -err);
@@ -77,7 +84,7 @@ void switch_to_tt(void *prev, void *next)
         change_sig(SIGALRM, alrm);
         change_sig(SIGPROF, prof);
 
-        arch_switch();
+        arch_switch_to_tt(prev_sched, current);
 
         flush_tlb_all();
         local_irq_restore(flags);
@@ -141,7 +148,6 @@ static void new_thread_handler(int sig)
         set_cmdline("(kernel thread)");
 
         change_sig(SIGUSR1, 1);
-        change_sig(SIGVTALRM, 1);
         change_sig(SIGPROF, 1);
         local_irq_enable();
         if(!run_kernel_thread(fn, arg, &current->thread.exec_buf))