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#include <sys/mman.h>
#include <sys/fcntl.h> /* for O_RDWR */
#include <sys/unistd.h>
#include <sched.h> /* for sched_yield() */
#include <stdio.h>
#include "litmus.h"
#include "internal.h"
#define LITMUS_CTRL_DEVICE "/dev/litmus/ctrl"
#define CTRL_PAGES 1
#define LITMUS_STATS_FILE "/proc/litmus/stats"
static int map_file(const char* filename, void **addr, size_t size)
{
int error = 0;
int fd;
if (size > 0) {
fd = open(filename, O_RDWR);
if (fd >= 0) {
*addr = mmap(NULL, size,
PROT_READ | PROT_WRITE,
MAP_PRIVATE,
fd, 0);
if (*addr == MAP_FAILED)
error = -1;
close(fd);
} else
error = fd;
} else
*addr = NULL;
return error;
}
ssize_t read_file(const char* fname, void* buf, size_t maxlen)
{
int fd;
ssize_t n = 0;
size_t got = 0;
fd = open(fname, O_RDONLY);
if (fd == -1)
return -1;
while (got < maxlen && (n = read(fd, buf + got, maxlen - got)) > 0)
got += n;
close(fd);
if (n < 0)
return -1;
else
return got;
}
int read_litmus_stats(int *ready, int *all)
{
char buf[100];
ssize_t len;
len = read_file(LITMUS_STATS_FILE, buf, sizeof(buf) - 1);
if (len >= 0)
len = sscanf(buf,
"real-time tasks = %d\n"
"ready for release = %d\n",
all, ready);
return len == 2;
}
int get_nr_ts_release_waiters(void)
{
int ready, all;
if (read_litmus_stats(&ready, &all))
return ready;
else
return -1;
}
/* thread-local pointer to control page */
static __thread struct control_page *ctrl_page;
int init_kernel_iface(void)
{
int err = 0;
long page_size = sysconf(_SC_PAGESIZE);
void* mapped_at = NULL;
BUILD_BUG_ON(sizeof(union np_flag) != sizeof(uint32_t));
BUILD_BUG_ON(offsetof(struct control_page, sched.raw)
!= LITMUS_CP_OFFSET_SCHED);
BUILD_BUG_ON(offsetof(struct control_page, irq_count)
!= LITMUS_CP_OFFSET_IRQ_COUNT);
BUILD_BUG_ON(offsetof(struct control_page, ts_syscall_start)
!= LITMUS_CP_OFFSET_TS_SC_START);
BUILD_BUG_ON(offsetof(struct control_page, irq_syscall_start)
!= LITMUS_CP_OFFSET_IRQ_SC_START);
err = map_file(LITMUS_CTRL_DEVICE, &mapped_at, CTRL_PAGES * page_size);
/* Assign ctrl_page indirectly to avoid GCC warnings about aliasing
* related to type pruning.
*/
ctrl_page = mapped_at;
if (err) {
fprintf(stderr, "%s: cannot open LITMUS^RT control page (%m)\n",
__FUNCTION__);
}
return err;
}
void enter_np(void)
{
if (likely(ctrl_page != NULL) || init_kernel_iface() == 0)
ctrl_page->sched.np.flag++;
else
fprintf(stderr, "enter_np: control page not mapped!\n");
}
void exit_np(void)
{
if (likely(ctrl_page != NULL) &&
ctrl_page->sched.np.flag &&
!(--ctrl_page->sched.np.flag)) {
/* became preemptive, let's check for delayed preemptions */
__sync_synchronize();
if (ctrl_page->sched.np.preempt)
sched_yield();
}
}
int requested_to_preempt(void)
{
return (likely(ctrl_page != NULL) && ctrl_page->sched.np.preempt);
}
/* init and return a ptr to the control page for
* preemption and migration overhead analysis
*
* FIXME it may be desirable to have a RO control page here
*/
struct control_page* get_ctrl_page(void)
{
if((ctrl_page != NULL) || init_kernel_iface() == 0)
return ctrl_page;
else
return NULL;
}
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