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Kernel+LibPthread+LibC: Add a naive futex and use it for pthread_cond_t

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This patch implements a simple version of the futex (fast userspace
mutex) API in the kernel and uses it to make the pthread_cond_t API's
block instead of busily sched_yield().

An arbitrary userspace address is passed to the kernel as a "token"
that identifies the futex and you can then FUTEX_WAIT and FUTEX_WAKE
that specific userspace address.

FUTEX_WAIT corresponds to pthread_cond_wait() and FUTEX_WAKE is used
for pthread_cond_signal() and pthread_cond_broadcast().

I'm pretty sure I'm missing something in this implementation, but it's
hopefully okay for a start. :^)
This commit is contained in:
Andreas Kling 2019-12-22 21:29:47 +01:00
parent 4b8b100b83
commit 4a8683ea68
9 changed files with 99 additions and 55 deletions
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8
Libraries/LibC/serenity.cpp
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@ -27,4 +27,12 @@ int profiling_disable(pid_t pid)
int rc = syscall(SC_profiling_disable, pid);
__RETURN_WITH_ERRNO(rc, rc, -1);
}
int futex(int32_t* userspace_address, int futex_op, int32_t value, const struct timespec* timeout)
{
Syscall::SC_futex_params params { userspace_address, futex_op, value, timeout };
int rc = syscall(SC_futex, &params);
__RETURN_WITH_ERRNO(rc, rc, -1);
}
}

5
Libraries/LibC/serenity.h
View file

@ -44,4 +44,9 @@ int module_unload(const char* name, size_t name_length);
int profiling_enable(pid_t);
int profiling_disable(pid_t);
#define FUTEX_WAIT 1
#define FUTEX_WAKE 2
int futex(int32_t* userspace_address, int futex_op, int32_t value, const struct timespec* timeout);
__END_DECLS

4
Libraries/LibC/sys/types.h
View file

@ -77,7 +77,9 @@ typedef struct __pthread_mutexattr_t {
} pthread_mutexattr_t;
typedef struct __pthread_cond_t {
void* storage;
int32_t value;
uint32_t previous;
int clockid; // clockid_t
} pthread_cond_t;
typedef void* pthread_rwlock_t;