spin.c File Reference

#include "postgres.h"
#include "storage/pg_sema.h"
#include "storage/shmem.h"
#include "storage/spin.h"

Include dependency graph for spin.c:

Go to the source code of this file.

Macros
#define	NUM_EMULATION_SEMAPHORES   (NUM_SPINLOCK_SEMAPHORES + NUM_ATOMICS_SEMAPHORES)

Functions
Size	SpinlockSemaSize (void)
int	SpinlockSemas (void)
void	SpinlockSemaInit (void)
static void	s_check_valid (int lockndx)
void	s_init_lock_sema (volatile slock_t *lock, bool nested)
void	s_unlock_sema (volatile slock_t *lock)
bool	s_lock_free_sema (volatile slock_t *lock)
int	tas_sema (volatile slock_t *lock)

Variables
PGSemaphore *	SpinlockSemaArray

Macro Definition Documentation

NUM_EMULATION_SEMAPHORES

#define NUM_EMULATION_SEMAPHORES   (NUM_SPINLOCK_SEMAPHORES + NUM_ATOMICS_SEMAPHORES)

Definition at line 37 of file spin.c.

Function Documentation

s_check_valid()

static void s_check_valid ( int  lockndx )

inlinestatic

Definition at line 114 of file spin.c.

{
    if (unlikely(lockndx <= 0 || lockndx > NUM_EMULATION_SEMAPHORES))
        elog(ERROR, "invalid spinlock number: %d", lockndx);
}

References elog(), ERROR, NUM_EMULATION_SEMAPHORES, and unlikely.

Referenced by s_init_lock_sema(), s_unlock_sema(), and tas_sema().

s_init_lock_sema()

void s_init_lock_sema	(	volatile slock_t *	lock,
		bool	nested
	)

Definition at line 121 of file spin.c.

{
    static uint32 counter = 0;
    uint32      offset;
    uint32      sema_total;
    uint32      idx;
 
    if (nested)
    {
        /*
         * To allow nesting atomics inside spinlocked sections, use a
         * different spinlock. See comment above.
         */
        offset = 1 + NUM_SPINLOCK_SEMAPHORES;
        sema_total = NUM_ATOMICS_SEMAPHORES;
    }
    else
    {
        offset = 1;
        sema_total = NUM_SPINLOCK_SEMAPHORES;
    }
 
    idx = (counter++ % sema_total) + offset;
 
    /* double check we did things correctly */
    s_check_valid(idx);
 
    *lock = idx;
}

References idx(), NUM_ATOMICS_SEMAPHORES, NUM_SPINLOCK_SEMAPHORES, and s_check_valid().

Referenced by pg_atomic_init_flag_impl(), pg_atomic_init_u32_impl(), and pg_atomic_init_u64_impl().

s_lock_free_sema()

bool s_lock_free_sema

(

volatile slock_t *

lock

)

Definition at line 162 of file spin.c.

{
    /* We don't currently use S_LOCK_FREE anyway */
    elog(ERROR, "spin.c does not support S_LOCK_FREE()");
    return false;
}

References elog(), and ERROR.

s_unlock_sema()

void s_unlock_sema

(

volatile slock_t *

lock

)

Definition at line 152 of file spin.c.

{
    int         lockndx = *lock;
 
    s_check_valid(lockndx);
 
    PGSemaphoreUnlock(SpinlockSemaArray[lockndx - 1]);
}

References PGSemaphoreUnlock(), s_check_valid(), and SpinlockSemaArray.

SpinlockSemaInit()

void SpinlockSemaInit

(

void

)

Definition at line 77 of file spin.c.

{
    PGSemaphore *spinsemas;
    int         nsemas = SpinlockSemas();
    int         i;
 
    /*
     * We must use ShmemAllocUnlocked(), since the spinlock protecting
     * ShmemAlloc() obviously can't be ready yet.
     */
    spinsemas = (PGSemaphore *) ShmemAllocUnlocked(SpinlockSemaSize());
    for (i = 0; i < nsemas; ++i)
        spinsemas[i] = PGSemaphoreCreate();
    SpinlockSemaArray = spinsemas;
}

References i, PGSemaphoreCreate(), ShmemAllocUnlocked(), SpinlockSemaArray, SpinlockSemas(), and SpinlockSemaSize().

Referenced by CreateSharedMemoryAndSemaphores().

SpinlockSemas()

int SpinlockSemas

(

void

)

Definition at line 64 of file spin.c.

{
    return NUM_EMULATION_SEMAPHORES;
}

References NUM_EMULATION_SEMAPHORES.

Referenced by CalculateShmemSize(), and SpinlockSemaInit().

SpinlockSemaSize()

Size SpinlockSemaSize

(

void

)

Definition at line 55 of file spin.c.

{
    return NUM_EMULATION_SEMAPHORES * sizeof(PGSemaphore);
}

References NUM_EMULATION_SEMAPHORES.

Referenced by CalculateShmemSize(), and SpinlockSemaInit().

tas_sema()

int tas_sema

(

volatile slock_t *

lock

)

Definition at line 170 of file spin.c.

{
    int         lockndx = *lock;
 
    s_check_valid(lockndx);
 
    /* Note that TAS macros return 0 if *success* */
    return !PGSemaphoreTryLock(SpinlockSemaArray[lockndx - 1]);
}

References PGSemaphoreTryLock(), s_check_valid(), and SpinlockSemaArray.

Variable Documentation

SpinlockSemaArray

PGSemaphore* SpinlockSemaArray

Definition at line 42 of file spin.c.

Referenced by s_unlock_sema(), SpinlockSemaInit(), and tas_sema().