void switch_to_tt(void *prev, void *next)
{
struct task_struct *from, *to, *prev_sched;
unsigned long flags;
int err, vtalrm, alrm, prof, cpu;
char c;
from = prev;
to = next;
cpu = from->thread_info->cpu;
if(cpu == 0)
forward_interrupts(to->thread.mode.tt.extern_pid);
#ifdef CONFIG_SMP
forward_ipi(cpu_data[cpu].ipi_pipe[0], to->thread.mode.tt.extern_pid);
#endif
local_irq_save(flags);
vtalrm = change_sig(SIGVTALRM, 0);
alrm = change_sig(SIGALRM, 0);
prof = change_sig(SIGPROF, 0);
forward_pending_sigio(to->thread.mode.tt.extern_pid);
c = 0;
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);
if(from->thread.mode.tt.switch_pipe[0] == -1)
os_kill_process(os_getpid(), 0);
err = os_read_file(from->thread.mode.tt.switch_pipe[0], &c, sizeof(c));
if(err != sizeof(c))
panic("read of switch_pipe failed, errno = %d", -err);
/* If the process that we have just scheduled away from has exited,
* then it needs to be killed here. The reason is that, even though
* it will kill itself when it next runs, that may be too late. Its
* stack will be freed, possibly before then, and if that happens,
* we have a use-after-free situation. So, it gets killed here
* in case it has not already killed itself.
*/
prev_sched = current->thread.prev_sched;
if(prev_sched->thread.mode.tt.switch_pipe[0] == -1)
os_kill_process(prev_sched->thread.mode.tt.extern_pid, 1);
change_sig(SIGVTALRM, vtalrm);
change_sig(SIGALRM, alrm);
change_sig(SIGPROF, prof);
arch_switch();
flush_tlb_all();
local_irq_restore(flags);
}
void switch_to_tt(void *prev, void *next)
{
struct task_struct *from, *to, *prev_sched;
unsigned long flags;
int err, vtalrm, alrm, prof, cpu;
char c;
from = prev;
to = next;
cpu = task_thread_info(from)->cpu;
if(cpu == 0)
forward_interrupts(to->thread.mode.tt.extern_pid);
#ifdef CONFIG_SMP
forward_ipi(cpu_data[cpu].ipi_pipe[0], to->thread.mode.tt.extern_pid);
#endif
local_irq_save(flags);
vtalrm = change_sig(SIGVTALRM, 0);
alrm = change_sig(SIGALRM, 0);
prof = change_sig(SIGPROF, 0);
forward_pending_sigio(to->thread.mode.tt.extern_pid);
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* "to", and can't use any more the value of "from" (which is outdated),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);
if(from->thread.mode.tt.switch_pipe[0] == -1)
os_kill_process(os_getpid(), 0);
err = os_read_file(from->thread.mode.tt.switch_pipe[0], &c, sizeof(c));
if(err != sizeof(c))
panic("read of switch_pipe failed, errno = %d", -err);
/* If the process that we have just scheduled away from has exited,
* then it needs to be killed here. The reason is that, even though
* it will kill itself when it next runs, that may be too late. Its
* stack will be freed, possibly before then, and if that happens,
* we have a use-after-free situation. So, it gets killed here
* in case it has not already killed itself.
*/
prev_sched = current->thread.prev_sched;
if(prev_sched->thread.mode.tt.switch_pipe[0] == -1)
os_kill_process(prev_sched->thread.mode.tt.extern_pid, 1);
change_sig(SIGVTALRM, vtalrm);
change_sig(SIGALRM, alrm);
change_sig(SIGPROF, prof);
arch_switch_to_tt(prev_sched, current);
flush_tlb_all();
local_irq_restore(flags);
}
void *switch_to_tt(void *prev, void *next, void *last)
{
struct task_struct *from, *to, *prev_sched;
unsigned long flags;
int err, vtalrm, alrm, prof, cpu;
char c;
/* jailing and SMP are incompatible, so this doesn't need to be
* made per-cpu
*/
static int reading;
from = prev;
to = next;
to->thread.prev_sched = from;
cpu = from->thread_info->cpu;
if(cpu == 0)
forward_interrupts(to->thread.mode.tt.extern_pid);
#ifdef CONFIG_SMP
forward_ipi(cpu_data[cpu].ipi_pipe[0], to->thread.mode.tt.extern_pid);
#endif
local_irq_save(flags);
vtalrm = change_sig(SIGVTALRM, 0);
alrm = change_sig(SIGALRM, 0);
prof = change_sig(SIGPROF, 0);
forward_pending_sigio(to->thread.mode.tt.extern_pid);
c = 0;
set_current(to);
reading = 0;
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);
reading = 1;
if((from->exit_state == EXIT_ZOMBIE) || (from->exit_state == EXIT_DEAD))
os_kill_process(os_getpid(), 0);
err = os_read_file(from->thread.mode.tt.switch_pipe[0], &c, sizeof(c));
if(err != sizeof(c))
panic("read of switch_pipe failed, errno = %d", -err);
/* If the process that we have just scheduled away from has exited,
* then it needs to be killed here. The reason is that, even though
* it will kill itself when it next runs, that may be too late. Its
* stack will be freed, possibly before then, and if that happens,
* we have a use-after-free situation. So, it gets killed here
* in case it has not already killed itself.
*/
prev_sched = current->thread.prev_sched;
if((prev_sched->exit_state == EXIT_ZOMBIE) ||
(prev_sched->exit_state == EXIT_DEAD))
os_kill_ptraced_process(prev_sched->thread.mode.tt.extern_pid, 1);
/* This works around a nasty race with 'jail'. If we are switching
* between two threads of a threaded app and the incoming process
* runs before the outgoing process reaches the read, and it makes
* it all the way out to userspace, then it will have write-protected
* the outgoing process stack. Then, when the outgoing process
* returns from the write, it will segfault because it can no longer
* write its own stack. So, in order to avoid that, the incoming
* thread sits in a loop yielding until 'reading' is set. This
* isn't entirely safe, since there may be a reschedule from a timer
* happening between setting 'reading' and sleeping in read. But,
* it should get a whole quantum in which to reach the read and sleep,
* which should be enough.
*/
if(jail){
while(!reading) sched_yield();
}
change_sig(SIGVTALRM, vtalrm);
change_sig(SIGALRM, alrm);
change_sig(SIGPROF, prof);
arch_switch();
flush_tlb_all();
local_irq_restore(flags);
return(current->thread.prev_sched);
}
