newlib-cygwin/winsup/cygserver/bsd_mutex.cc

385 lines
10 KiB
C++

/* bsd_mutex.cc
This file is part of Cygwin.
This software is a copyrighted work licensed under the terms of the
Cygwin license. Please consult the file "CYGWIN_LICENSE" for
details. */
#ifdef __OUTSIDE_CYGWIN__
#include "woutsup.h"
#include <errno.h>
#define _KERNEL 1
#define __BSD_VISIBLE 1
#include <sys/smallprint.h>
#include <limits.h>
#include <stdlib.h>
#include <sys/msg.h>
#include <sys/sem.h>
#include "process.h"
#include "cygserver_ipc.h"
/* A BSD kernel global mutex. */
struct mtx Giant;
void
mtx_init (mtx *m, const char *name, const void *, int)
{
m->name = name;
m->owner = 0;
m->cnt = 0;
/* Can't use Windows Mutexes here since Windows Mutexes are only
unlockable by the lock owner. */
m->h = CreateSemaphore (NULL, 1, 1, NULL);
if (!m->h)
panic ("couldn't allocate %s mutex, %u\n", name, GetLastError ());
}
void
_mtx_lock (mtx *m, DWORD winpid, const char *file, int line)
{
_debug (file, line, "Try locking mutex %s (%u) (hold: %u)",
m->name, winpid, m->owner);
if (WaitForSingleObject (m->h, INFINITE) != WAIT_OBJECT_0)
_panic (file, line, "wait for %s in %d failed, %u", m->name, winpid,
GetLastError ());
m->owner = winpid;
_debug (file, line, "Locked mutex %s/%u (owner: %u)",
m->name, ++m->cnt, winpid);
}
int
mtx_owned (mtx *m, DWORD winpid)
{
return m->owner == winpid;
}
void
_mtx_assert (mtx *m, int what, DWORD winpid, const char *file, int line)
{
switch (what)
{
case MA_OWNED:
if (!mtx_owned (m, winpid))
_panic (file, line, "Mutex %s not owned", m->name);
break;
case MA_NOTOWNED:
if (mtx_owned (m, winpid))
_panic (file, line, "Mutex %s is owned", m->name);
break;
default:
break;
}
}
void
_mtx_unlock (mtx *m, const char *file, int line)
{
DWORD owner = m->owner;
unsigned long cnt = m->cnt;
m->owner = 0;
/* Cautiously check if mtx_destroy has been called (shutdown).
In that case, m->h is NULL. */
if (m->h && !ReleaseSemaphore (m->h, 1, NULL))
{
/* Check if the semaphore was already on it's max value. */
if (GetLastError () != ERROR_TOO_MANY_POSTS)
_panic (file, line, "release of mutex %s failed, %u", m->name,
GetLastError ());
}
_debug (file, line, "Unlocked mutex %s/%u (owner: %u)",
m->name, cnt, owner);
}
void
mtx_destroy (mtx *m)
{
HANDLE tmp = m->h;
m->h = NULL;
if (tmp)
CloseHandle (tmp);
}
/*
* Helper functions for msleep/wakeup.
*/
static int
win_priority (int priority)
{
int p = (int)((priority) & PRIO_MASK) - PZERO;
/* Generating a valid priority value is a bit tricky. The only valid
values on NT4 are -15, -2, -1, 0, 1, 2, 15. */
switch (p)
{
case -15: case -14: case -13: case -12: case -11:
return THREAD_PRIORITY_IDLE;
case -10: case -9: case -8: case -7: case -6:
return THREAD_PRIORITY_LOWEST;
case -5: case -4: case -3: case -2: case -1:
return THREAD_PRIORITY_BELOW_NORMAL;
case 0:
return THREAD_PRIORITY_NORMAL;
case 1: case 2: case 3: case 4: case 5:
return THREAD_PRIORITY_ABOVE_NORMAL;
case 6: case 7: case 8: case 9: case 10:
return THREAD_PRIORITY_HIGHEST;
case 11: case 12: case 13: case 14: case 15:
return THREAD_PRIORITY_TIME_CRITICAL;
}
return THREAD_PRIORITY_NORMAL;
}
/*
* Sets the thread priority, returns the old priority.
*/
static int
set_priority (int priority)
{
int old_prio = GetThreadPriority (GetCurrentThread ());
if (!SetThreadPriority (GetCurrentThread (), win_priority (priority)))
log (LOG_WARNING,
"Warning: Setting thread priority to %d failed with error %u\n",
win_priority (priority), GetLastError ());
return old_prio;
}
/*
* Original description from BSD code:
*
* General sleep call. Suspends the current process until a wakeup is
* performed on the specified identifier. The process will then be made
* runnable with the specified priority. Sleeps at most timo/hz seconds
* (0 means no timeout). If pri includes PCATCH flag, signals are checked
* before and after sleeping, else signals are not checked. Returns 0 if
* awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a
* signal needs to be delivered, ERESTART is returned if the current system
* call should be restarted if possible, and EINTR is returned if the system
* call should be interrupted by the signal (return EINTR).
*
* The mutex argument is exited before the caller is suspended, and
* entered before msleep returns. If priority includes the PDROP
* flag the mutex is not entered before returning.
*/
static HANDLE msleep_glob_evt;
class msleep_sync_array
{
enum msleep_action {
MSLEEP_ENTER = 0,
MSLEEP_LEAVE,
MSLEEP_WAKEUP
};
CRITICAL_SECTION cs;
long cnt;
long max_cnt;
struct msleep_record {
void *ident;
HANDLE wakeup_evt;
LONG threads;
} *a;
int find_ident (void *ident, msleep_action action)
{
int i;
for (i = 0; i < cnt; ++i)
if (a[i].ident == ident)
return i;
if (i >= max_cnt)
panic ("ident %x not found and run out of slots.", ident);
if (i >= cnt && action == MSLEEP_LEAVE)
panic ("ident %x not found (%d).", ident, action);
return i;
}
HANDLE first_entry (int i, void *ident)
{
debug ("New ident %x, index %d", ident, i);
a[i].ident = ident;
a[i].wakeup_evt = CreateEvent (NULL, TRUE, FALSE, NULL);
if (!a[i].wakeup_evt)
panic ("CreateEvent failed: %u", GetLastError ());
debug ("i = %d, CreateEvent: %x", i, a[i].wakeup_evt);
a[i].threads = 1;
++cnt;
return a[i].wakeup_evt;
}
HANDLE next_entry (int i)
{
if (a[i].ident && WaitForSingleObject (a[i].wakeup_evt, 0) != WAIT_OBJECT_0)
{
++a[i].threads;
return a[i].wakeup_evt;
}
return NULL;
}
public:
msleep_sync_array (int count) : cnt (0), max_cnt (count)
{
InitializeCriticalSection (&cs);
if (!(a = new msleep_record[count]))
panic ("Allocating msleep records failed: %d", errno);
}
~msleep_sync_array () { delete a; }
HANDLE enter (void *ident)
{
HANDLE evt = NULL;
while (!evt)
{
EnterCriticalSection (&cs);
int i = find_ident (ident, MSLEEP_ENTER);
if (i >= cnt)
evt = first_entry (i, ident);
else if (!(evt = next_entry (i)))
{
/* wakeup has been called, so sleep to wait until all
formerly waiting threads have left and retry. */
LeaveCriticalSection (&cs);
Sleep (1L);
}
}
LeaveCriticalSection (&cs);
return evt;
}
void leave (void *ident)
{
EnterCriticalSection (&cs);
int i = find_ident (ident, MSLEEP_LEAVE);
if (--a[i].threads == 0)
{
debug ("i = %d, CloseEvent: %x", i, a[i].wakeup_evt);
CloseHandle (a[i].wakeup_evt);
a[i].ident = NULL;
--cnt;
if (i < cnt)
a[i] = a[cnt];
}
LeaveCriticalSection (&cs);
}
void wakeup (void *ident)
{
EnterCriticalSection (&cs);
int i = find_ident (ident, MSLEEP_WAKEUP);
if (i < cnt && a[i].ident)
SetEvent (a[i].wakeup_evt);
LeaveCriticalSection (&cs);
}
};
static msleep_sync_array *msleep_sync;
extern struct msginfo msginfo;
extern struct seminfo seminfo;
void
msleep_init (void)
{
msleep_glob_evt = CreateEvent (NULL, TRUE, FALSE, NULL);
if (!msleep_glob_evt)
panic ("CreateEvent in msleep_init failed: %u", GetLastError ());
int32_t msgmni = support_msgqueues ? msginfo.msgmni : 0;
int32_t semmni = support_semaphores ? seminfo.semmni : 0;
TUNABLE_INT_FETCH ("kern.ipc.msgmni", &msgmni);
TUNABLE_INT_FETCH ("kern.ipc.semmni", &semmni);
debug ("Try allocating msgmni (%d) + semmni (%d) msleep records",
msgmni, semmni);
msleep_sync = new msleep_sync_array (msgmni + semmni);
if (!msleep_sync)
panic ("Allocating msleep records in msleep_init failed: %d", errno);
}
int
_msleep (void *ident, struct mtx *mtx, int priority,
const char *wmesg, int timo, struct thread *td)
{
int ret = -1;
HANDLE evt = msleep_sync->enter (ident);
if (mtx)
mtx_unlock (mtx);
int old_priority = set_priority (priority);
HANDLE obj[4] =
{
evt,
msleep_glob_evt,
td->client->handle (),
td->ipcblk->signal_arrived
};
/* PCATCH handling. If PCATCH is given and signal_arrived is a valid
handle, then it's used in the WaitFor call and EINTR is returned. */
int obj_cnt = 3;
if ((priority & PCATCH) && obj[3])
obj_cnt = 4;
switch (WaitForMultipleObjects (obj_cnt, obj, FALSE, timo ?: INFINITE))
{
case WAIT_OBJECT_0: /* wakeup() has been called. */
ret = 0;
debug ("msleep wakeup called for %d", td->td_proc->winpid);
break;
case WAIT_OBJECT_0 + 1: /* Shutdown event (triggered by wakeup_all). */
priority |= PDROP;
fallthrough;
case WAIT_OBJECT_0 + 2: /* The dependent process has exited. */
debug ("msleep process exit or shutdown for %d", td->td_proc->winpid);
ret = EIDRM;
break;
case WAIT_OBJECT_0 + 3: /* Signal for calling process arrived. */
debug ("msleep process got signal for %d", td->td_proc->winpid);
ret = EINTR;
break;
case WAIT_TIMEOUT:
ret = EWOULDBLOCK;
break;
default:
/* There's a chance that a process has been terminated before
WaitForMultipleObjects has been called. In this case the handles
might be invalid. The error code returned is ERROR_INVALID_HANDLE.
Since we can trust the values of these handles otherwise, we
treat an ERROR_INVALID_HANDLE as a normal process termination and
hope for the best. */
if (GetLastError () != ERROR_INVALID_HANDLE)
panic ("wait in msleep (%s) failed, %u", wmesg, GetLastError ());
debug ("wait in msleep (%s) failed for %d, %u", wmesg,
td->td_proc->winpid, GetLastError ());
ret = EIDRM;
break;
}
msleep_sync->leave (ident);
set_priority (old_priority);
if (mtx && !(priority & PDROP))
mtx_lock (mtx);
return ret;
}
/*
* Make all threads sleeping on the specified identifier runnable.
*/
int
wakeup (void *ident)
{
msleep_sync->wakeup (ident);
return 0;
}
/*
* Wakeup all sleeping threads. Only called in the context of cygserver
* shutdown.
*/
void
wakeup_all (void)
{
SetEvent (msleep_glob_evt);
}
#endif /* __OUTSIDE_CYGWIN__ */