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Kernel: Some futex improvements

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This adds support for FUTEX_WAKE_OP, FUTEX_WAIT_BITSET, FUTEX_WAKE_BITSET,
FUTEX_REQUEUE, and FUTEX_CMP_REQUEUE, as well well as global and private
futex and absolute/relative timeouts against the appropriate clock. This
also changes the implementation so that kernel resources are only used when
a thread is blocked on a futex.

Global futexes are implemented as offsets in VMObjects, so that different
processes can share a futex against the same VMObject despite potentially
being mapped at different virtual addresses.
This commit is contained in:
Tom 2020-12-21 23:21:58 -07:00 • committed by Andreas Kling
parent 7581b64705
commit 1d621ab172
23 changed files with 928 additions and 63 deletions
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11
Kernel/Process.h
View file

@ -38,6 +38,7 @@
#include <Kernel/API/Syscall.h>
#include <Kernel/FileSystem/InodeMetadata.h>
#include <Kernel/Forward.h>
#include <Kernel/FutexQueue.h>
#include <Kernel/Lock.h>
#include <Kernel/ProcessGroup.h>
#include <Kernel/StdLib.h>
@ -94,6 +95,8 @@ enum class VeilState {
Locked,
};
typedef HashMap<FlatPtr, RefPtr<FutexQueue>> FutexQueues;
class Process
: public RefCounted<Process>
, public InlineLinkedListNode<Process>
@ -542,6 +545,8 @@ private:
bool has_tracee_thread(ProcessID tracer_pid);
void clear_futex_queues_on_exec();
RefPtr<PageDirectory> m_page_directory;
Process* m_prev { nullptr };
@ -637,11 +642,11 @@ private:
VeilState m_veil_state { VeilState::None };
UnveilNode m_unveiled_paths { "/", { .full_path = "/", .unveil_inherited_from_root = true } };
WaitQueue& futex_queue(Userspace<const i32*>);
HashMap<u32, OwnPtr<WaitQueue>> m_futex_queues;
OwnPtr<PerformanceEventBuffer> m_perf_event_buffer;
FutexQueues m_futex_queues;
SpinLock<u8> m_futex_lock;
// This member is used in the implementation of ptrace's PT_TRACEME flag.
// If it is set to true, the process will stop at the next execve syscall
// and wait for a tracer to attach.