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https://github.com/RGBCube/serenity
synced 2025-05-31 10:38:11 +00:00
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
Andreas Kling
parent
d53e54f8bf
commit
6aa77d1999
4 changed files with 170 additions and 150 deletions
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@ -6,6 +6,7 @@ KERNEL_OBJS = \
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StdLib.o \
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Arch/i386/CPU.o \
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Process.o \
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SharedBuffer.o \
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Thread.o \
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Arch/i386/PIT.o \
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Devices/KeyboardDevice.o \
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@ -20,9 +20,9 @@
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#include <Kernel/RTC.h>
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#include <Kernel/Scheduler.h>
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#include <Kernel/StdLib.h>
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#include <Kernel/SharedBuffer.h>
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#include <Kernel/Syscall.h>
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#include <Kernel/TTY/MasterPTY.h>
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#include <Kernel/VM/MemoryManager.h>
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#include <Kernel/kmalloc.h>
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#include <LibC/errno_numbers.h>
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#include <LibC/signal_numbers.h>
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@ -2366,155 +2366,6 @@ int Process::sys$setsockopt(const Syscall::SC_setsockopt_params* params)
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return socket.setsockopt(level, option, value, value_size);
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}
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struct SharedBuffer {
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private:
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struct Reference {
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Reference(pid_t pid)
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: pid(pid)
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{
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}
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pid_t pid;
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unsigned count { 1 };
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Region* region { nullptr };
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};
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public:
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SharedBuffer(int id, int size)
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: m_shared_buffer_id(id)
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, m_vmo(VMObject::create_anonymous(size))
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{
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#ifdef SHARED_BUFFER_DEBUG
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dbgprintf("Created shared buffer %d of size %d\n", m_shared_buffer_id, size);
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#endif
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}
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~SharedBuffer()
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{
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#ifdef SHARED_BUFFER_DEBUG
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dbgprintf("Destroyed shared buffer %d of size %d\n", m_shared_buffer_id, size());
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#endif
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}
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bool is_shared_with(pid_t peer_pid)
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{
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LOCKER(m_refs.lock());
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for (auto& ref : m_refs.resource()) {
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if (ref.pid == peer_pid) {
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return true;
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}
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}
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return false;
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}
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void* get_address(Process& process)
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{
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LOCKER(m_refs.lock());
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ASSERT(is_shared_with(process.pid()));
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for (auto& ref : m_refs.resource()) {
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if (ref.pid == process.pid()) {
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if (ref.region == nullptr) {
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ref.region = process.allocate_region_with_vmo(VirtualAddress(), size(), m_vmo, 0, "SharedBuffer", PROT_READ | (m_writable ? PROT_WRITE : 0));
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ref.region->set_shared(true);
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}
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return ref.region->vaddr().as_ptr();
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}
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}
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ASSERT_NOT_REACHED();
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}
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void share_with(pid_t peer_pid)
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{
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LOCKER(m_refs.lock());
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for (auto& ref : m_refs.resource()) {
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if (ref.pid == peer_pid) {
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ref.count++;
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return;
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}
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}
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m_refs.resource().append(Reference(peer_pid));
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}
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void release(Process& process)
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{
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LOCKER(m_refs.lock());
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#ifdef SHARED_BUFFER_DEBUG
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dbgprintf("Releasing shared buffer %d of size %d by PID %d\n", m_shared_buffer_id, size(), process.pid());
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#endif
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for (int i = 0; i < m_refs.resource().size(); ++i) {
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auto& ref = m_refs.resource()[i];
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if (ref.pid == process.pid()) {
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if (--ref.count == 0) {
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process.deallocate_region(*ref.region);
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m_refs.resource().remove(i);
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destroy_if_unused();
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return;
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}
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}
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}
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}
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void disown(pid_t pid)
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{
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LOCKER(m_refs.lock());
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#ifdef SHARED_BUFFER_DEBUG
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dbgprintf("Disowning shared buffer %d of size %d by PID %d\n", m_shared_buffer_id, size(), pid);
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#endif
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for (int i = 0; i < m_refs.resource().size(); ++i) {
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auto& ref = m_refs.resource()[i];
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if (ref.pid == pid) {
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m_refs.resource().remove(i);
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destroy_if_unused();
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return;
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}
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}
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}
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size_t size() const { return m_vmo->size(); }
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void destroy_if_unused();
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void seal()
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{
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LOCKER(m_refs.lock());
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m_writable = false;
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for (auto& ref : m_refs.resource()) {
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if (ref.region) {
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ref.region->set_writable(false);
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MM.remap_region(*ref.region->page_directory(), *ref.region);
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}
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}
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}
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int m_shared_buffer_id { -1 };
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bool m_writable { true };
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NonnullRefPtr<VMObject> m_vmo;
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Lockable<Vector<Reference, 2>> m_refs;
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};
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static int s_next_shared_buffer_id;
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Lockable<HashMap<int, OwnPtr<SharedBuffer>>>& shared_buffers()
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{
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static Lockable<HashMap<int, OwnPtr<SharedBuffer>>>* map;
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if (!map)
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map = new Lockable<HashMap<int, OwnPtr<SharedBuffer>>>;
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return *map;
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}
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void SharedBuffer::destroy_if_unused()
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{
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LOCKER(m_refs.lock());
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if (m_refs.resource().size() == 0) {
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LOCKER(shared_buffers().lock());
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#ifdef SHARED_BUFFER_DEBUG
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kprintf("Destroying unused SharedBuffer{%p} id: %d\n", this, m_shared_buffer_id);
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#endif
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auto count_before = shared_buffers().resource().size();
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shared_buffers().resource().remove(m_shared_buffer_id);
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ASSERT(count_before != shared_buffers().resource().size());
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}
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}
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void Process::disown_all_shared_buffers()
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{
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LOCKER(shared_buffers().lock());
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@ -2542,6 +2393,7 @@ int Process::sys$create_shared_buffer(pid_t peer_pid, int size, void** buffer)
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return -ESRCH;
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}
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LOCKER(shared_buffers().lock());
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static int s_next_shared_buffer_id;
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int shared_buffer_id = ++s_next_shared_buffer_id;
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auto shared_buffer = make<SharedBuffer>(shared_buffer_id, size);
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shared_buffer->share_with(m_pid);
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117
Kernel/SharedBuffer.cpp
Normal file
117
Kernel/SharedBuffer.cpp
Normal file
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@ -0,0 +1,117 @@
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#include <Kernel/SharedBuffer.h>
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#include <Kernel/Process.h>
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Lockable<HashMap<int, OwnPtr<SharedBuffer>>>& shared_buffers()
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{
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static Lockable<HashMap<int, OwnPtr<SharedBuffer>>>* map;
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if (!map)
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map = new Lockable<HashMap<int, OwnPtr<SharedBuffer>>>;
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return *map;
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}
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bool SharedBuffer::is_shared_with(pid_t peer_pid)
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{
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LOCKER(shared_buffers().lock());
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for (auto& ref : m_refs) {
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if (ref.pid == peer_pid) {
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return true;
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}
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}
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return false;
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}
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void* SharedBuffer::get_address(Process& process)
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{
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LOCKER(shared_buffers().lock());
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ASSERT(is_shared_with(process.pid()));
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for (auto& ref : m_refs) {
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if (ref.pid == process.pid()) {
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if (ref.region == nullptr) {
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ref.region = process.allocate_region_with_vmo(VirtualAddress(), size(), m_vmo, 0, "SharedBuffer", PROT_READ | (m_writable ? PROT_WRITE : 0));
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ref.region->set_shared(true);
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}
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return ref.region->vaddr().as_ptr();
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}
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}
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ASSERT_NOT_REACHED();
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}
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void SharedBuffer::share_with(pid_t peer_pid)
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{
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LOCKER(shared_buffers().lock());
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for (auto& ref : m_refs) {
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if (ref.pid == peer_pid) {
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ref.count++;
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return;
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}
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}
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m_refs.append(Reference(peer_pid));
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}
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void SharedBuffer::release(Process& process)
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{
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LOCKER(shared_buffers().lock());
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for (int i = 0; i < m_refs.size(); ++i) {
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auto& ref = m_refs[i];
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if (ref.pid == process.pid()) {
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if (--ref.count == 0) {
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#ifdef SHARED_BUFFER_DEBUG
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dbgprintf("Releasing shared buffer reference on %d of size %d by PID %d\n", m_shared_buffer_id, size(), process.pid());
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#endif
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process.deallocate_region(*ref.region);
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m_refs.remove(i);
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#ifdef SHARED_BUFFER_DEBUG
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dbgprintf("Released shared buffer reference on %d of size %d by PID %d\n", m_shared_buffer_id, size(), process.pid());
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#endif
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destroy_if_unused();
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return;
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}
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}
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}
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}
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void SharedBuffer::disown(pid_t pid)
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{
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LOCKER(shared_buffers().lock());
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for (int i = 0; i < m_refs.size(); ++i) {
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auto& ref = m_refs[i];
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if (ref.pid == pid) {
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#ifdef SHARED_BUFFER_DEBUG
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dbgprintf("Disowning shared buffer %d of size %d by PID %d\n", m_shared_buffer_id, size(), pid);
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#endif
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m_refs.remove(i);
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#ifdef SHARED_BUFFER_DEBUG
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dbgprintf("Disowned shared buffer %d of size %d by PID %d\n", m_shared_buffer_id, size(), pid);
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#endif
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destroy_if_unused();
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return;
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}
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}
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}
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void SharedBuffer::destroy_if_unused()
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{
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LOCKER(shared_buffers().lock());
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if (m_refs.size() == 0) {
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#ifdef SHARED_BUFFER_DEBUG
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kprintf("Destroying unused SharedBuffer{%p} id: %d\n", this, m_shared_buffer_id);
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#endif
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auto count_before = shared_buffers().resource().size();
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shared_buffers().resource().remove(m_shared_buffer_id);
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ASSERT(count_before != shared_buffers().resource().size());
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}
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}
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void SharedBuffer::seal()
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{
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LOCKER(shared_buffers().lock());
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m_writable = false;
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for (auto& ref : m_refs) {
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if (ref.region) {
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ref.region->set_writable(false);
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MM.remap_region(*ref.region->page_directory(), *ref.region);
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}
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}
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}
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50
Kernel/SharedBuffer.h
Normal file
50
Kernel/SharedBuffer.h
Normal file
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@ -0,0 +1,50 @@
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#pragma once
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#include <Kernel/VM/MemoryManager.h>
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#include <AK/OwnPtr.h>
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struct SharedBuffer {
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private:
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struct Reference {
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Reference(pid_t pid)
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: pid(pid)
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{
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}
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pid_t pid;
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unsigned count { 1 };
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Region* region { nullptr };
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};
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public:
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SharedBuffer(int id, int size)
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: m_shared_buffer_id(id)
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, m_vmo(VMObject::create_anonymous(size))
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{
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#ifdef SHARED_BUFFER_DEBUG
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dbgprintf("Created shared buffer %d of size %d\n", m_shared_buffer_id, size);
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#endif
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}
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~SharedBuffer()
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{
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#ifdef SHARED_BUFFER_DEBUG
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dbgprintf("Destroyed shared buffer %d of size %d\n", m_shared_buffer_id, size());
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#endif
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}
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bool is_shared_with(pid_t peer_pid);
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void* get_address(Process& process);
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void share_with(pid_t peer_pid);
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void release(Process& process);
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void disown(pid_t pid);
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size_t size() const { return m_vmo->size(); }
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void destroy_if_unused();
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void seal();
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int m_shared_buffer_id { -1 };
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bool m_writable { true };
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NonnullRefPtr<VMObject> m_vmo;
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Vector<Reference, 2> m_refs;
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};
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Lockable<HashMap<int, OwnPtr<SharedBuffer>>>& shared_buffers();
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