procsignal.c File Reference

#include "postgres.h"
#include <signal.h>
#include <unistd.h>
#include "access/parallel.h"
#include "commands/async.h"
#include "miscadmin.h"
#include "replication/walsender.h"
#include "storage/ipc.h"
#include "storage/latch.h"
#include "storage/proc.h"
#include "storage/shmem.h"
#include "storage/sinval.h"
#include "tcop/tcopprot.h"

Include dependency graph for procsignal.c:

Go to the source code of this file.

Data Structures
struct	ProcSignalSlot

Macros
#define	NumProcSignalSlots   (MaxBackends + NUM_AUXPROCTYPES)

Functions
static bool	CheckProcSignal (ProcSignalReason reason)
static void	CleanupProcSignalState (int status, Datum arg)
Size	ProcSignalShmemSize (void)
void	ProcSignalShmemInit (void)
void	ProcSignalInit (int pss_idx)
int	SendProcSignal (pid_t pid, ProcSignalReason reason, BackendId backendId)
void	procsignal_sigusr1_handler (SIGNAL_ARGS)

Variables
static ProcSignalSlot *	ProcSignalSlots = NULL
static volatile ProcSignalSlot *	MyProcSignalSlot = NULL

Macro Definition Documentation

NumProcSignalSlots

#define NumProcSignalSlots   (MaxBackends + NUM_AUXPROCTYPES)

Definition at line 60 of file procsignal.c.

Referenced by ProcSignalInit(), ProcSignalShmemSize(), and SendProcSignal().

Function Documentation

CheckProcSignal()

static bool CheckProcSignal ( ProcSignalReason  reason )

static

Definition at line 239 of file procsignal.c.

References MyProcSignalSlot, and ProcSignalSlot::pss_signalFlags.

Referenced by procsignal_sigusr1_handler().

{
    volatile ProcSignalSlot *slot = MyProcSignalSlot;

    if (slot != NULL)
    {
        /* Careful here --- don't clear flag if we haven't seen it set */
        if (slot->pss_signalFlags[reason])
        {
            slot->pss_signalFlags[reason] = false;
            return true;
        }
    }

    return false;
}

CleanupProcSignalState()

static void CleanupProcSignalState ( int  status, Datum  arg  )

static

Definition at line 137 of file procsignal.c.

References Assert, DatumGetInt32, elog, LOG, MyProcPid, and ProcSignalSlot::pss_pid.

Referenced by ProcSignalInit().

{
    int         pss_idx = DatumGetInt32(arg);
    volatile ProcSignalSlot *slot;

    slot = &ProcSignalSlots[pss_idx - 1];
    Assert(slot == MyProcSignalSlot);

    /*
     * Clear MyProcSignalSlot, so that a SIGUSR1 received after this point
     * won't try to access it after it's no longer ours (and perhaps even
     * after we've unmapped the shared memory segment).
     */
    MyProcSignalSlot = NULL;

    /* sanity check */
    if (slot->pss_pid != MyProcPid)
    {
        /*
         * don't ERROR here. We're exiting anyway, and don't want to get into
         * infinite loop trying to exit
         */
        elog(LOG, "process %d releasing ProcSignal slot %d, but it contains %d",
             MyProcPid, pss_idx, (int) slot->pss_pid);
        return;                 /* XXX better to zero the slot anyway? */
    }

    slot->pss_pid = 0;
}

procsignal_sigusr1_handler()

void procsignal_sigusr1_handler

(

SIGNAL_ARGS

)

Definition at line 260 of file procsignal.c.

References CheckProcSignal(), HandleCatchupInterrupt(), HandleNotifyInterrupt(), HandleParallelMessageInterrupt(), HandleWalSndInitStopping(), latch_sigusr1_handler(), MyLatch, PROCSIG_CATCHUP_INTERRUPT, PROCSIG_NOTIFY_INTERRUPT, PROCSIG_PARALLEL_MESSAGE, PROCSIG_RECOVERY_CONFLICT_BUFFERPIN, PROCSIG_RECOVERY_CONFLICT_DATABASE, PROCSIG_RECOVERY_CONFLICT_LOCK, PROCSIG_RECOVERY_CONFLICT_SNAPSHOT, PROCSIG_RECOVERY_CONFLICT_STARTUP_DEADLOCK, PROCSIG_RECOVERY_CONFLICT_TABLESPACE, PROCSIG_WALSND_INIT_STOPPING, RecoveryConflictInterrupt(), and SetLatch().

Referenced by autoprewarm_main(), AutoVacLauncherMain(), AutoVacWorkerMain(), BackgroundWriterMain(), CheckpointerMain(), PostgresMain(), StartBackgroundWorker(), StartupProcessMain(), WalReceiverMain(), WalSndSignals(), and WalWriterMain().

{
    int         save_errno = errno;

    if (CheckProcSignal(PROCSIG_CATCHUP_INTERRUPT))
        HandleCatchupInterrupt();

    if (CheckProcSignal(PROCSIG_NOTIFY_INTERRUPT))
        HandleNotifyInterrupt();

    if (CheckProcSignal(PROCSIG_PARALLEL_MESSAGE))
        HandleParallelMessageInterrupt();

    if (CheckProcSignal(PROCSIG_WALSND_INIT_STOPPING))
        HandleWalSndInitStopping();

    if (CheckProcSignal(PROCSIG_RECOVERY_CONFLICT_DATABASE))
        RecoveryConflictInterrupt(PROCSIG_RECOVERY_CONFLICT_DATABASE);

    if (CheckProcSignal(PROCSIG_RECOVERY_CONFLICT_TABLESPACE))
        RecoveryConflictInterrupt(PROCSIG_RECOVERY_CONFLICT_TABLESPACE);

    if (CheckProcSignal(PROCSIG_RECOVERY_CONFLICT_LOCK))
        RecoveryConflictInterrupt(PROCSIG_RECOVERY_CONFLICT_LOCK);

    if (CheckProcSignal(PROCSIG_RECOVERY_CONFLICT_SNAPSHOT))
        RecoveryConflictInterrupt(PROCSIG_RECOVERY_CONFLICT_SNAPSHOT);

    if (CheckProcSignal(PROCSIG_RECOVERY_CONFLICT_STARTUP_DEADLOCK))
        RecoveryConflictInterrupt(PROCSIG_RECOVERY_CONFLICT_STARTUP_DEADLOCK);

    if (CheckProcSignal(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN))
        RecoveryConflictInterrupt(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN);

    SetLatch(MyLatch);

    latch_sigusr1_handler();

    errno = save_errno;
}

ProcSignalInit()

void ProcSignalInit

(

int

pss_idx

)

Definition at line 104 of file procsignal.c.

References Assert, CleanupProcSignalState(), elog, Int32GetDatum, LOG, MemSet, MyProcPid, NUM_PROCSIGNALS, NumProcSignalSlots, on_shmem_exit(), ProcSignalSlot::pss_pid, and ProcSignalSlot::pss_signalFlags.

Referenced by AuxiliaryProcessMain(), and InitPostgres().

{
    volatile ProcSignalSlot *slot;

    Assert(pss_idx >= 1 && pss_idx <= NumProcSignalSlots);

    slot = &ProcSignalSlots[pss_idx - 1];

    /* sanity check */
    if (slot->pss_pid != 0)
        elog(LOG, "process %d taking over ProcSignal slot %d, but it's not empty",
             MyProcPid, pss_idx);

    /* Clear out any leftover signal reasons */
    MemSet(slot->pss_signalFlags, 0, NUM_PROCSIGNALS * sizeof(sig_atomic_t));

    /* Mark slot with my PID */
    slot->pss_pid = MyProcPid;

    /* Remember slot location for CheckProcSignal */
    MyProcSignalSlot = slot;

    /* Set up to release the slot on process exit */
    on_shmem_exit(CleanupProcSignalState, Int32GetDatum(pss_idx));
}

ProcSignalShmemInit()

void ProcSignalShmemInit

(

void

)

Definition at line 83 of file procsignal.c.

References MemSet, ProcSignalShmemSize(), and ShmemInitStruct().

Referenced by CreateSharedMemoryAndSemaphores().

{
    Size        size = ProcSignalShmemSize();
    bool        found;

    ProcSignalSlots = (ProcSignalSlot *)
        ShmemInitStruct("ProcSignalSlots", size, &found);

    /* If we're first, set everything to zeroes */
    if (!found)
        MemSet(ProcSignalSlots, 0, size);
}

ProcSignalShmemSize()

Size ProcSignalShmemSize

(

void

)

Definition at line 73 of file procsignal.c.

References NumProcSignalSlots.

Referenced by CreateSharedMemoryAndSemaphores(), and ProcSignalShmemInit().

{
    return NumProcSignalSlots * sizeof(ProcSignalSlot);
}

SendProcSignal()

int SendProcSignal	(	pid_t	pid,
		ProcSignalReason	reason,
		BackendId	backendId
	)

Definition at line 179 of file procsignal.c.

References i, InvalidBackendId, kill, NumProcSignalSlots, ProcSignalSlot::pss_pid, ProcSignalSlot::pss_signalFlags, and SIGUSR1.

Referenced by CancelDBBackends(), CancelVirtualTransaction(), mq_putmessage(), ParallelWorkerShutdown(), SICleanupQueue(), SignalBackends(), and WalSndInitStopping().

{
    volatile ProcSignalSlot *slot;

    if (backendId != InvalidBackendId)
    {
        slot = &ProcSignalSlots[backendId - 1];

        /*
         * Note: Since there's no locking, it's possible that the target
         * process detaches from shared memory and exits right after this
         * test, before we set the flag and send signal. And the signal slot
         * might even be recycled by a new process, so it's remotely possible
         * that we set a flag for a wrong process. That's OK, all the signals
         * are such that no harm is done if they're mistakenly fired.
         */
        if (slot->pss_pid == pid)
        {
            /* Atomically set the proper flag */
            slot->pss_signalFlags[reason] = true;
            /* Send signal */
            return kill(pid, SIGUSR1);
        }
    }
    else
    {
        /*
         * BackendId not provided, so search the array using pid.  We search
         * the array back to front so as to reduce search overhead.  Passing
         * InvalidBackendId means that the target is most likely an auxiliary
         * process, which will have a slot near the end of the array.
         */
        int         i;

        for (i = NumProcSignalSlots - 1; i >= 0; i--)
        {
            slot = &ProcSignalSlots[i];

            if (slot->pss_pid == pid)
            {
                /* the above note about race conditions applies here too */

                /* Atomically set the proper flag */
                slot->pss_signalFlags[reason] = true;
                /* Send signal */
                return kill(pid, SIGUSR1);
            }
        }
    }

    errno = ESRCH;
    return -1;
}

Variable Documentation

MyProcSignalSlot

volatile ProcSignalSlot* MyProcSignalSlot = NULL

static

Definition at line 63 of file procsignal.c.

Referenced by CheckProcSignal().

ProcSignalSlots

ProcSignalSlot* ProcSignalSlots = NULL

static

Definition at line 62 of file procsignal.c.