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Fix race condition in wait_for_termination

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If preempted, it was possible for a process to be waiting forever
This commit is contained in:
Baptiste Wicht 2016-07-03 15:59:54 +02:00
parent 1c3af14f35
commit 27dc7e25a0
1 changed files with 14 additions and 0 deletions
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14
kernel/src/scheduler.cpp
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@ -26,6 +26,7 @@
#include "mutex.hpp"
#include "kernel_utils.hpp"
#include "logging.hpp"
#include "int_lock.hpp"
//Provided by task_switch.s
extern "C" {
@ -690,23 +691,35 @@ void scheduler::sbrk(size_t inc){
}
void scheduler::await_termination(pid_t pid){
int_lock lock;
while(true){
lock.acquire();
bool found = false;
for(auto& process : pcb){
if(process.process.ppid == current_pid && process.process.pid == pid){
if(process.state == process_state::KILLED){
lock.release();
return;
}
found = true;
break;
}
}
// The process may have already been cleaned, we can simply return
if(!found){
lock.release();
return;
}
logging::logf(logging::log_level::DEBUG, "Process %u waits for %u\n", current_pid, pid);
pcb[current_pid].state = process_state::WAITING;
lock.release();
reschedule();
}
}
@ -726,6 +739,7 @@ void scheduler::kill_current_process(){
unblock_process(gc_pid);
pcb[current_pid].state = scheduler::process_state::KILLED;
logging::logf(logging::log_level::DEBUG, "Found%u\n", static_cast<uint8_t>(pcb[current_pid].state));
//Run another process
reschedule();