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