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Kernel: Make waitpid() block by default unless WNOHANG is specified

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This commit is contained in:
apio 2022-10-27 17:05:42 +02:00
parent da8a3de480
commit fcf53ef6a5
7 changed files with 163 additions and 25 deletions
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5
apps/src/init.c
View File

@ -60,10 +60,7 @@ int main()
for (;;)
{
while ((result = wait(NULL)) == 0) // No child has exited yet
{
msleep(100);
}
result = wait(NULL);
if (result == child) return 0;
}
}

3
apps/src/sh.c
View File

@ -169,8 +169,7 @@ void command_execute(command* cmd)
perror(argv[0]);
exit(127);
}
pid_t result;
while ((result = waitpid(child, &status, 0)) == 0) { msleep(20); }
pid_t result = waitpid(child, &status, 0);
if (result < 0)
{
perror("waitpid");

37
kernel/include/thread/Task.h
View File

@ -7,6 +7,13 @@
#define TASK_MAX_FDS 32
enum class BlockReason
{
None,
Reading,
Waiting,
};
struct Task
{
enum TaskState
@ -69,16 +76,32 @@ struct Task
char name[128];
struct
{
size_t size;
int fd;
char* buf;
} blocking_read_info;
BlockReason block_reason;
void resume_read();
union {
struct
{
size_t size;
int fd;
char* buf;
} blocking_read_info;
struct
{
int64_t wait_pid;
int* wstatus;
} blocking_wait_info;
};
void resume();
bool is_still_blocking();
Descriptor* descriptor_from_fd(int fd, int& error);
private:
void resume_read();
void resume_wait();
bool is_read_still_blocking();
bool is_wait_still_blocking();
};

1
kernel/src/sys/stdio.cpp
View File

@ -255,6 +255,7 @@ void sys_read(Context* context, int fd, size_t size, char* buffer)
}
Task* current_task = Scheduler::current_task();
current_task->state = current_task->Blocking;
current_task->block_reason = BlockReason::Reading;
current_task->blocking_read_info.fd = fd;
current_task->blocking_read_info.buf = (char*)VMM::get_physical((uint64_t)buffer); // FIXME: Handle errors.
current_task->blocking_read_info.size = size;

110
kernel/src/thread/Scheduler.cpp
View File

@ -404,11 +404,7 @@ void Scheduler::task_yield(Context* context)
sched_current_task = sched_current_task->next_task;
if (sched_current_task->state == sched_current_task->Blocking)
{
if (!sched_current_task->is_still_blocking())
{
sched_current_task->resume_read();
sched_current_task->state = sched_current_task->Running;
}
if (!sched_current_task->is_still_blocking()) sched_current_task->resume();
}
if (sched_current_task->state == sched_current_task->Running)
{
@ -464,8 +460,10 @@ Task* Scheduler::current_task()
return sched_current_task;
}
#define WNOHANG 1
void sys_waitpid(Context* context, long pid, int* wstatus,
int) // FIXME: Use the value in options and block if WNOHANG has not been specified.
int options) // FIXME: only allow waiting for child processes when specifying a PID.
{
Task* child = nullptr;
if (pid == -1)
@ -480,8 +478,29 @@ void sys_waitpid(Context* context, long pid, int* wstatus,
});
if (!child)
{
context->rax = 0; // No child has exited, let's return 0.
return;
if (options & WNOHANG)
{
context->rax = 0; // No child has exited, let's return 0.
return;
}
int* kwstatus;
if (wstatus)
{
kwstatus = obtain_user_ref(wstatus);
if (!kwstatus)
{
context->rax = -EFAULT;
return;
}
}
kdbgln("blocking wait on any child");
sched_current_task->state = sched_current_task->Blocking;
sched_current_task->block_reason = BlockReason::Waiting;
sched_current_task->blocking_wait_info.wait_pid = -1;
if (wstatus) sched_current_task->blocking_wait_info.wstatus = kwstatus;
else
sched_current_task->blocking_wait_info.wstatus = nullptr;
return Scheduler::task_yield(context);
}
}
else
@ -493,10 +512,31 @@ void sys_waitpid(Context* context, long pid, int* wstatus,
return;
}
}
if (child->state != child->Dying) // FIXME: This should block if WNOHANG has not been specified.
if (child->state != child->Dying)
{
context->rax = 0;
return;
if (options & WNOHANG)
{
context->rax = 0; // No child has exited, let's return 0.
return;
}
int* kwstatus;
if (wstatus)
{
kwstatus = obtain_user_ref(wstatus);
if (!kwstatus)
{
context->rax = -EFAULT;
return;
}
}
kdbgln("blocking wait on pid %ld", pid);
sched_current_task->state = sched_current_task->Blocking;
sched_current_task->block_reason = BlockReason::Waiting;
sched_current_task->blocking_wait_info.wait_pid = pid;
if (wstatus) sched_current_task->blocking_wait_info.wstatus = kwstatus;
else
sched_current_task->blocking_wait_info.wstatus = nullptr;
return Scheduler::task_yield(context);
}
if (wstatus)
{
@ -518,6 +558,54 @@ void sys_waitpid(Context* context, long pid, int* wstatus,
context->rax = (long)child->id;
}
bool Task::is_wait_still_blocking()
{
Task* child = nullptr;
if (blocking_wait_info.wait_pid == -1)
{
sched_for_each_child(sched_current_task, [&](Task* task) {
if (task->state == task->Dying)
{
child = task;
return false;
}
return true;
});
if (!child) return true;
else
{
blocking_wait_info.wait_pid = child->id; // We're committed to this child now.
return false;
}
}
else
{
child = Scheduler::find_by_pid(blocking_wait_info.wait_pid);
if (child->state != child->Dying) return true;
else
return false;
}
}
void Task::resume_wait()
{
ASSERT(blocking_wait_info.wait_pid != -1); // is_wait_still_blocking should have chosen a child for us if the user
// process told us to wait for any child.
Task* child = Scheduler::find_by_pid(blocking_wait_info.wait_pid);
ASSERT(child); // This should also already have been validated.
kdbgln("resuming wait on child %ld", child->id);
if (blocking_wait_info.wstatus)
{
*blocking_wait_info.wstatus = (int)(child->exit_status & 0xff);
release_user_ref(blocking_wait_info.wstatus);
}
child->state = child->Exited;
regs.rax = (long)child->id;
}
struct pstat
{
long pt_pid;

29
kernel/src/thread/Task.cpp
View File

@ -3,6 +3,7 @@
#include "thread/Task.h"
#include "log/Log.h"
#include "memory/VMM.h"
#include "std/assert.h"
#include "std/errno.h"
#include "std/string.h"
@ -80,11 +81,37 @@ void Task::resume_read()
VMM::apply_address_space();
}
bool Task::is_still_blocking()
bool Task::is_read_still_blocking()
{
return VFS::would_block(files[blocking_read_info.fd].node());
}
void Task::resume()
{
switch (block_reason)
{
case BlockReason::None: ASSERT(false);
case BlockReason::Reading: resume_read(); break;
case BlockReason::Waiting: resume_wait(); break;
default: ASSERT(false);
}
block_reason = BlockReason::None;
state = Running;
}
bool Task::is_still_blocking()
{
switch (block_reason)
{
case BlockReason::None: ASSERT(false);
case BlockReason::Reading: return is_read_still_blocking();
case BlockReason::Waiting: return is_wait_still_blocking();
default: ASSERT(false);
}
}
Descriptor* Task::descriptor_from_fd(int fd, int& error)
{
if (fd < 0 || fd >= TASK_MAX_FDS)

3
libs/libc/include/sys/wait.h
View File

@ -9,6 +9,9 @@
/* What was the child's exit status? */
#define WEXITSTATUS(status) (char)((status)&0xff)
/* Do not block the current process if no child has exited. */
#define WNOHANG 1
#ifdef __cplusplus
extern "C"
{