mirror of
https://github.com/genodelabs/genode.git
synced 2025-03-10 22:44:30 +00:00
841a1fd579
The kernel provides a "recall" feature issued on threads to force a thread into an exception. In the exception the current state of the thread can be obtained and its execution can be halted/paused. However, the recall exception is only delivered when the next time the thread would leave the kernel. That means the delivery is asynchronous and Genode has to wait until the exception triggered. Waiting for the exception can either be done in the cpu_session service or outside the service in the protection domain of the caller. It turned out that waiting inside the cpu_service is prone to deadlock the system. The cpu_session interface is one of many session interfaces handled by the same thread inside Core. Deadlock situation: * The caller (thread_c) to pause some thread_p manages to establish the call to the cpu_session thread_s of Core but get be interrupted before issuing the actual pause (recall) command. * Now the - to be recalled thread_p - is scheduled and tries to invoke another service of Core, like making log output. * Since the Core thread_s is handling the session request of thread_c, the kernel uses the timeslice of thread_p to help to finish the request handled by thread_s. * Thread_s issues the actual pause/recall on thread_p and blocks inside Core to wait for the recall exception to be issued. * thread_p will leave not the kernel before finishing it actual IPC with thread_s which is blocked waiting for thread_p. That is the reason why the waiting/blocking for the recall exception taking place must be done on NOVA in the context of the caller (thread_1). Introduce a pause_sync call to the cpu_session which returns a semaphore capability to the caller. The caller blocks on the semaphore and is woken up when the pager of thread_p receives the recall exception with the state of thread_p.
100 lines
2.8 KiB
C++
100 lines
2.8 KiB
C++
/*
|
|
* \brief Client-side cpu session NOVA extension
|
|
* \author Alexander Boettcher
|
|
* \date 2012-07-27
|
|
*/
|
|
|
|
/*
|
|
* Copyright (C) 2012-2012 Genode Labs GmbH
|
|
*
|
|
* This file is part of the Genode OS framework, which is distributed
|
|
* under the terms of the GNU General Public License version 2.
|
|
*/
|
|
|
|
#ifndef _INCLUDE__CPU_SESSION__CLIENT_H_
|
|
#define _INCLUDE__CPU_SESSION__CLIENT_H_
|
|
|
|
#include <base/rpc_client.h>
|
|
#include <base/thread.h>
|
|
|
|
#include <cpu_session/capability.h>
|
|
|
|
#include <nova_cpu_session/nova_cpu_session.h>
|
|
|
|
namespace Genode {
|
|
|
|
struct Cpu_session_client : Rpc_client<Nova_cpu_session>
|
|
{
|
|
explicit Cpu_session_client(Cpu_session_capability session)
|
|
: Rpc_client<Nova_cpu_session>(static_cap_cast<Nova_cpu_session>(session)) { }
|
|
|
|
Thread_capability create_thread(Name const &name, addr_t utcb = 0) {
|
|
return call<Rpc_create_thread>(name, utcb); }
|
|
|
|
Ram_dataspace_capability utcb(Thread_capability thread) {
|
|
return call<Rpc_utcb>(thread); }
|
|
|
|
|
|
void kill_thread(Thread_capability thread) {
|
|
call<Rpc_kill_thread>(thread); }
|
|
|
|
Thread_capability first() {
|
|
return call<Rpc_first>(); }
|
|
|
|
Thread_capability next(Thread_capability curr) {
|
|
return call<Rpc_next>(curr); }
|
|
|
|
int set_pager(Thread_capability thread, Pager_capability pager) {
|
|
return call<Rpc_set_pager>(thread, pager); }
|
|
|
|
int start(Thread_capability thread, addr_t ip, addr_t sp) {
|
|
return call<Rpc_start>(thread, ip, sp); }
|
|
|
|
void pause(Thread_capability thread)
|
|
{
|
|
Native_capability block = call<Rpc_pause_sync>(thread);
|
|
if (!block.valid())
|
|
return;
|
|
|
|
Nova::sm_ctrl(block.local_name(), Nova::SEMAPHORE_DOWN);
|
|
|
|
Nova::revoke(Nova::Obj_crd(block.local_name(), 0));
|
|
cap_selector_allocator()->free(block.local_name(), 0);
|
|
}
|
|
|
|
void resume(Thread_capability thread) {
|
|
call<Rpc_resume>(thread); }
|
|
|
|
void cancel_blocking(Thread_capability thread) {
|
|
call<Rpc_cancel_blocking>(thread); }
|
|
|
|
int state(Thread_capability thread, Thread_state *dst_state) {
|
|
return call<Rpc_state>(thread, dst_state); }
|
|
|
|
void exception_handler(Thread_capability thread, Signal_context_capability handler) {
|
|
call<Rpc_exception_handler>(thread, handler); }
|
|
|
|
void single_step(Thread_capability thread, bool enable) {
|
|
call<Rpc_single_step>(thread, enable); }
|
|
|
|
Native_capability native_cap(Thread_capability cap) {
|
|
return call<Rpc_native_cap>(cap); }
|
|
|
|
int start_exc_base_vcpu(Thread_capability thread, addr_t ip,
|
|
addr_t sp, addr_t exc_base,
|
|
bool vcpu = false)
|
|
{
|
|
return call<Rpc_start_exc_base_vcpu>(thread, ip, sp,
|
|
exc_base, vcpu);
|
|
}
|
|
|
|
private:
|
|
|
|
Native_capability pause_sync(Thread_capability target) {
|
|
return Native_capability::invalid_cap(); }
|
|
|
|
};
|
|
}
|
|
|
|
#endif /* _INCLUDE__CPU_SESSION__CLIENT_H_ */
|