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SharedBuffer: Fix deadlock on destroy

We were locking the list of references, and then destroying the
reference, which made things go a little crazy.

It's more straightforward to just remove the per-reference lock: the
syscalls all have to lock the full list anyway, so let's just do that
and avoid the hassle.

While I'm at it, also move the SharedBuffer code out to its own file as it's
getting a little long and unwieldly, and Process.cpp is already huge.
This commit is contained in:
Robin Burchell 2019-07-16 15:03:39 +02:00 committed by Andreas Kling
parent d53e54f8bf
commit 6aa77d1999
4 changed files with 170 additions and 150 deletions

50
Kernel/SharedBuffer.h Normal file
View file

@ -0,0 +1,50 @@
#pragma once
#include <Kernel/VM/MemoryManager.h>
#include <AK/OwnPtr.h>
struct SharedBuffer {
private:
struct Reference {
Reference(pid_t pid)
: pid(pid)
{
}
pid_t pid;
unsigned count { 1 };
Region* region { nullptr };
};
public:
SharedBuffer(int id, int size)
: m_shared_buffer_id(id)
, m_vmo(VMObject::create_anonymous(size))
{
#ifdef SHARED_BUFFER_DEBUG
dbgprintf("Created shared buffer %d of size %d\n", m_shared_buffer_id, size);
#endif
}
~SharedBuffer()
{
#ifdef SHARED_BUFFER_DEBUG
dbgprintf("Destroyed shared buffer %d of size %d\n", m_shared_buffer_id, size());
#endif
}
bool is_shared_with(pid_t peer_pid);
void* get_address(Process& process);
void share_with(pid_t peer_pid);
void release(Process& process);
void disown(pid_t pid);
size_t size() const { return m_vmo->size(); }
void destroy_if_unused();
void seal();
int m_shared_buffer_id { -1 };
bool m_writable { true };
NonnullRefPtr<VMObject> m_vmo;
Vector<Reference, 2> m_refs;
};
Lockable<HashMap<int, OwnPtr<SharedBuffer>>>& shared_buffers();