win32_sema.c File Reference

#include "postgres.h"
#include "miscadmin.h"
#include "storage/ipc.h"
#include "storage/pg_sema.h"

Include dependency graph for win32_sema.c:

Go to the source code of this file.

Functions
static void	ReleaseSemaphores (int code, Datum arg)
void	PGSemaphoreShmemRequest (int maxSemas)
void	PGSemaphoreInit (int maxSemas)
PGSemaphore	PGSemaphoreCreate (void)
void	PGSemaphoreReset (PGSemaphore sema)
void	PGSemaphoreLock (PGSemaphore sema)
void	PGSemaphoreUnlock (PGSemaphore sema)
bool	PGSemaphoreTryLock (PGSemaphore sema)

Variables
static HANDLE *	mySemSet
static int	numSems
static int	maxSems

Function Documentation

PGSemaphoreCreate()

PGSemaphore PGSemaphoreCreate

(

void

)

Definition at line 78 of file win32_sema.c.

{
    HANDLE      cur_handle;
    SECURITY_ATTRIBUTES sec_attrs;
 
    /* Can't do this in a backend, because static state is postmaster's */
    Assert(!IsUnderPostmaster);
 
    if (numSems >= maxSems)
        elog(PANIC, "too many semaphores created");
 
    ZeroMemory(&sec_attrs, sizeof(sec_attrs));
    sec_attrs.nLength = sizeof(sec_attrs);
    sec_attrs.lpSecurityDescriptor = NULL;
    sec_attrs.bInheritHandle = TRUE;
 
    /* We don't need a named semaphore */
    cur_handle = CreateSemaphore(&sec_attrs, 1, 32767, NULL);
    if (cur_handle)
    {
        /* Successfully done */
        mySemSet[numSems++] = cur_handle;
    }
    else
        ereport(PANIC,
                (errmsg("could not create semaphore: error code %lu",
                        GetLastError())));
 
    return (PGSemaphore) cur_handle;
}

References Assert, elog, ereport, errmsg, fb(), IsUnderPostmaster, maxSems, mySemSet, numSems, and PANIC.

PGSemaphoreInit()

void PGSemaphoreInit

(

int

maxSemas

)

Definition at line 46 of file win32_sema.c.

{
    mySemSet = (HANDLE *) malloc(maxSemas * sizeof(HANDLE));
    if (mySemSet == NULL)
        elog(PANIC, "out of memory");
    numSems = 0;
    maxSems = maxSemas;
 
    on_shmem_exit(ReleaseSemaphores, 0);
}

References elog, fb(), malloc, maxSems, mySemSet, numSems, on_shmem_exit(), PANIC, and ReleaseSemaphores().

PGSemaphoreLock()

void PGSemaphoreLock

(

PGSemaphore

sema

)

Definition at line 131 of file win32_sema.c.

{
    HANDLE      wh[2];
    bool        done = false;
 
    /*
     * Note: pgwin32_signal_event should be first to ensure that it will be
     * reported when multiple events are set.  We want to guarantee that
     * pending signals are serviced.
     */
    wh[0] = pgwin32_signal_event;
    wh[1] = sema;
 
    /*
     * As in other implementations of PGSemaphoreLock, we need to check for
     * cancel/die interrupts each time through the loop.  But here, there is
     * no hidden magic about whether the syscall will internally service a
     * signal --- we do that ourselves.
     */
    while (!done)
    {
        DWORD       rc;
 
        CHECK_FOR_INTERRUPTS();
 
        rc = WaitForMultipleObjectsEx(2, wh, FALSE, INFINITE, TRUE);
        switch (rc)
        {
            case WAIT_OBJECT_0:
                /* Signal event is set - we have a signal to deliver */
                pgwin32_dispatch_queued_signals();
                break;
            case WAIT_OBJECT_0 + 1:
                /* We got it! */
                done = true;
                break;
            case WAIT_IO_COMPLETION:
 
                /*
                 * The system interrupted the wait to execute an I/O
                 * completion routine or asynchronous procedure call in this
                 * thread.  PostgreSQL does not provoke either of these, but
                 * atypical loaded DLLs or even other processes might do so.
                 * Now, resume waiting.
                 */
                break;
            case WAIT_FAILED:
                ereport(FATAL,
                        (errmsg("could not lock semaphore: error code %lu",
                                GetLastError())));
                break;
            default:
                elog(FATAL, "unexpected return code from WaitForMultipleObjectsEx(): %lu", rc);
                break;
        }
    }
}

References CHECK_FOR_INTERRUPTS, elog, ereport, errmsg, FATAL, fb(), pgwin32_dispatch_queued_signals(), and pgwin32_signal_event.

PGSemaphoreReset()

void PGSemaphoreReset

(

PGSemaphore

sema

)

Definition at line 115 of file win32_sema.c.

{
    /*
     * There's no direct API for this in Win32, so we have to ratchet the
     * semaphore down to 0 with repeated trylock's.
     */
    while (PGSemaphoreTryLock(sema))
         /* loop */ ;
}

References PGSemaphoreTryLock().

PGSemaphoreShmemRequest()

void PGSemaphoreShmemRequest

(

int

maxSemas

)

Definition at line 31 of file win32_sema.c.

{
    /* No shared memory needed on Windows */
}

PGSemaphoreTryLock()

bool PGSemaphoreTryLock

(

PGSemaphore

sema

)

Definition at line 209 of file win32_sema.c.

{
    DWORD       ret;
 
    ret = WaitForSingleObject(sema, 0);
 
    if (ret == WAIT_OBJECT_0)
    {
        /* We got it! */
        return true;
    }
    else if (ret == WAIT_TIMEOUT)
    {
        /* Can't get it */
        errno = EAGAIN;
        return false;
    }
 
    /* Otherwise we are in trouble */
    ereport(FATAL,
            (errmsg("could not try-lock semaphore: error code %lu",
                    GetLastError())));
 
    /* keep compiler quiet */
    return false;
}

References EAGAIN, ereport, errmsg, FATAL, and fb().

Referenced by PGSemaphoreReset().

PGSemaphoreUnlock()

void PGSemaphoreUnlock

(

PGSemaphore

sema

)

Definition at line 195 of file win32_sema.c.

{
    if (!ReleaseSemaphore(sema, 1, NULL))
        ereport(FATAL,
                (errmsg("could not unlock semaphore: error code %lu",
                        GetLastError())));
}

References ereport, errmsg, FATAL, and fb().

ReleaseSemaphores()

static void ReleaseSemaphores ( int  code, Datum  arg  )

static

Definition at line 63 of file win32_sema.c.

{
    int         i;
 
    for (i = 0; i < numSems; i++)
        CloseHandle(mySemSet[i]);
    free(mySemSet);
}

References fb(), free, i, mySemSet, and numSems.

Referenced by PGSemaphoreInit().

Variable Documentation

maxSems

int maxSems

static

Definition at line 22 of file win32_sema.c.

Referenced by PGSemaphoreCreate(), and PGSemaphoreInit().

mySemSet

HANDLE* mySemSet

static

Definition at line 20 of file win32_sema.c.

Referenced by PGSemaphoreCreate(), PGSemaphoreInit(), and ReleaseSemaphores().

numSems

int numSems

static

Definition at line 21 of file win32_sema.c.

Referenced by PGSemaphoreCreate(), PGSemaphoreInit(), and ReleaseSemaphores().