pmsignal.c File Reference

#include "postgres.h"
#include <signal.h>
#include <unistd.h>
#include "miscadmin.h"
#include "postmaster/postmaster.h"
#include "replication/walsender.h"
#include "storage/ipc.h"
#include "storage/pmsignal.h"
#include "storage/shmem.h"
#include "utils/memutils.h"

Include dependency graph for pmsignal.c:

Go to the source code of this file.

Data Structures
struct	PMSignalData

Macros
#define	PM_CHILD_UNUSED   0 /* these values must fit in sig_atomic_t */
#define	PM_CHILD_ASSIGNED   1
#define	PM_CHILD_ACTIVE   2
#define	PM_CHILD_WALSENDER   3

Functions
static void	MarkPostmasterChildInactive (int code, Datum arg)
Size	PMSignalShmemSize (void)
void	PMSignalShmemInit (void)
void	SendPostmasterSignal (PMSignalReason reason)
bool	CheckPostmasterSignal (PMSignalReason reason)
void	SetQuitSignalReason (QuitSignalReason reason)
QuitSignalReason	GetQuitSignalReason (void)
int	AssignPostmasterChildSlot (void)
bool	ReleasePostmasterChildSlot (int slot)
bool	IsPostmasterChildWalSender (int slot)
void	RegisterPostmasterChildActive (void)
void	MarkPostmasterChildWalSender (void)
bool	PostmasterIsAliveInternal (void)
void	PostmasterDeathSignalInit (void)

Variables
NON_EXEC_STATIC volatile PMSignalData *	PMSignalState = NULL
static int	num_child_inuse
static int	next_child_inuse
static bool *	PMChildInUse

Macro Definition Documentation

PM_CHILD_ACTIVE

#define PM_CHILD_ACTIVE   2

Definition at line 68 of file pmsignal.c.

PM_CHILD_ASSIGNED

#define PM_CHILD_ASSIGNED   1

Definition at line 67 of file pmsignal.c.

PM_CHILD_UNUSED

#define PM_CHILD_UNUSED   0 /* these values must fit in sig_atomic_t */

Definition at line 66 of file pmsignal.c.

PM_CHILD_WALSENDER

#define PM_CHILD_WALSENDER   3

Definition at line 69 of file pmsignal.c.

Function Documentation

AssignPostmasterChildSlot()

int AssignPostmasterChildSlot

(

void

)

Definition at line 250 of file pmsignal.c.

{
    int         slot = next_child_inuse;
    int         n;
 
    /*
     * Scan for a free slot.  Notice that we trust nothing about the contents
     * of PMSignalState, but use only postmaster-local data for this decision.
     * We track the last slot assigned so as not to waste time repeatedly
     * rescanning low-numbered slots.
     */
    for (n = num_child_inuse; n > 0; n--)
    {
        if (--slot < 0)
            slot = num_child_inuse - 1;
        if (!PMChildInUse[slot])
        {
            PMChildInUse[slot] = true;
            PMSignalState->PMChildFlags[slot] = PM_CHILD_ASSIGNED;
            next_child_inuse = slot;
            return slot + 1;
        }
    }
 
    /* Out of slots ... should never happen, else postmaster.c messed up */
    elog(FATAL, "no free slots in PMChildFlags array");
    return 0;                   /* keep compiler quiet */
}

References elog, FATAL, next_child_inuse, num_child_inuse, PM_CHILD_ASSIGNED, PMSignalData::PMChildFlags, PMChildInUse, and PMSignalState.

Referenced by assign_backendlist_entry(), BackendStartup(), and StartAutovacuumWorker().

CheckPostmasterSignal()

bool CheckPostmasterSignal

(

PMSignalReason

reason

)

Definition at line 201 of file pmsignal.c.

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

References PMSignalData::PMSignalFlags, and PMSignalState.

Referenced by process_pm_pmsignal().

GetQuitSignalReason()

QuitSignalReason GetQuitSignalReason

(

void

)

Definition at line 232 of file pmsignal.c.

{
    /* This is called in signal handlers, so be extra paranoid. */
    if (!IsUnderPostmaster || PMSignalState == NULL)
        return PMQUIT_NOT_SENT;
    return PMSignalState->sigquit_reason;
}

References IsUnderPostmaster, PMQUIT_NOT_SENT, PMSignalState, and PMSignalData::sigquit_reason.

Referenced by quickdie().

IsPostmasterChildWalSender()

bool IsPostmasterChildWalSender

(

int

slot

)

Definition at line 310 of file pmsignal.c.

{
    Assert(slot > 0 && slot <= num_child_inuse);
    slot--;
 
    if (PMSignalState->PMChildFlags[slot] == PM_CHILD_WALSENDER)
        return true;
    else
        return false;
}

References Assert, num_child_inuse, PM_CHILD_WALSENDER, PMSignalData::PMChildFlags, and PMSignalState.

Referenced by CountChildren(), and SignalSomeChildren().

MarkPostmasterChildInactive()

static void MarkPostmasterChildInactive ( int  code, Datum  arg  )

static

Definition at line 365 of file pmsignal.c.

{
    int         slot = MyPMChildSlot;
 
    Assert(slot > 0 && slot <= PMSignalState->num_child_flags);
    slot--;
    Assert(PMSignalState->PMChildFlags[slot] == PM_CHILD_ACTIVE ||
           PMSignalState->PMChildFlags[slot] == PM_CHILD_WALSENDER);
    PMSignalState->PMChildFlags[slot] = PM_CHILD_ASSIGNED;
}

References Assert, MyPMChildSlot, PM_CHILD_ACTIVE, PM_CHILD_ASSIGNED, PM_CHILD_WALSENDER, PMSignalData::PMChildFlags, and PMSignalState.

Referenced by RegisterPostmasterChildActive().

MarkPostmasterChildWalSender()

void MarkPostmasterChildWalSender

(

void

)

Definition at line 348 of file pmsignal.c.

{
    int         slot = MyPMChildSlot;
 
    Assert(am_walsender);
 
    Assert(slot > 0 && slot <= PMSignalState->num_child_flags);
    slot--;
    Assert(PMSignalState->PMChildFlags[slot] == PM_CHILD_ACTIVE);
    PMSignalState->PMChildFlags[slot] = PM_CHILD_WALSENDER;
}

References am_walsender, Assert, MyPMChildSlot, PM_CHILD_ACTIVE, PM_CHILD_WALSENDER, PMSignalData::PMChildFlags, and PMSignalState.

PMSignalShmemInit()

void PMSignalShmemInit

(

void

)

Definition at line 147 of file pmsignal.c.

{
    bool        found;
 
    PMSignalState = (PMSignalData *)
        ShmemInitStruct("PMSignalState", PMSignalShmemSize(), &found);
 
    if (!found)
    {
        /* initialize all flags to zeroes */
        MemSet(unvolatize(PMSignalData *, PMSignalState), 0, PMSignalShmemSize());
        num_child_inuse = MaxLivePostmasterChildren();
        PMSignalState->num_child_flags = num_child_inuse;
 
        /*
         * Also allocate postmaster's private PMChildInUse[] array.  We
         * might've already done that in a previous shared-memory creation
         * cycle, in which case free the old array to avoid a leak.  (Do it
         * like this to support the possibility that MaxLivePostmasterChildren
         * changed.)  In a standalone backend, we do not need this.
         */
        if (PostmasterContext != NULL)
        {
            if (PMChildInUse)
                pfree(PMChildInUse);
            PMChildInUse = (bool *)
                MemoryContextAllocZero(PostmasterContext,
                                       num_child_inuse * sizeof(bool));
        }
        next_child_inuse = 0;
    }
}

References MaxLivePostmasterChildren(), MemoryContextAllocZero(), MemSet, next_child_inuse, PMSignalData::num_child_flags, num_child_inuse, pfree(), PMChildInUse, PMSignalShmemSize(), PMSignalState, PostmasterContext, ShmemInitStruct(), and unvolatize.

Referenced by CreateOrAttachShmemStructs().

PMSignalShmemSize()

Size PMSignalShmemSize

(

void

)

Definition at line 132 of file pmsignal.c.

{
    Size        size;
 
    size = offsetof(PMSignalData, PMChildFlags);
    size = add_size(size, mul_size(MaxLivePostmasterChildren(),
                                   sizeof(sig_atomic_t)));
 
    return size;
}

References add_size(), MaxLivePostmasterChildren(), mul_size(), and size.

Referenced by CalculateShmemSize(), and PMSignalShmemInit().

PostmasterDeathSignalInit()

void PostmasterDeathSignalInit

(

void

)

Definition at line 446 of file pmsignal.c.

{
#ifdef USE_POSTMASTER_DEATH_SIGNAL
    int         signum = POSTMASTER_DEATH_SIGNAL;
 
    /* Register our signal handler. */
    pqsignal(signum, postmaster_death_handler);
 
    /* Request a signal on parent exit. */
#if defined(PR_SET_PDEATHSIG)
    if (prctl(PR_SET_PDEATHSIG, signum) < 0)
        elog(ERROR, "could not request parent death signal: %m");
#elif defined(PROC_PDEATHSIG_CTL)
    if (procctl(P_PID, 0, PROC_PDEATHSIG_CTL, &signum) < 0)
        elog(ERROR, "could not request parent death signal: %m");
#else
#error "USE_POSTMASTER_DEATH_SIGNAL set, but there is no mechanism to request the signal"
#endif
 
    /*
     * Just in case the parent was gone already and we missed it, we'd better
     * check the slow way on the first call.
     */
    postmaster_possibly_dead = true;
#endif                          /* USE_POSTMASTER_DEATH_SIGNAL */
}

References elog, ERROR, and pqsignal().

Referenced by InitPostmasterChild().

PostmasterIsAliveInternal()

bool PostmasterIsAliveInternal

(

void

)

Definition at line 385 of file pmsignal.c.

{
#ifdef USE_POSTMASTER_DEATH_SIGNAL
    /*
     * Reset the flag before checking, so that we don't miss a signal if
     * postmaster dies right after the check.  If postmaster was indeed dead,
     * we'll re-arm it before returning to caller.
     */
    postmaster_possibly_dead = false;
#endif
 
#ifndef WIN32
    {
        char        c;
        ssize_t     rc;
 
        rc = read(postmaster_alive_fds[POSTMASTER_FD_WATCH], &c, 1);
 
        /*
         * In the usual case, the postmaster is still alive, and there is no
         * data in the pipe.
         */
        if (rc < 0 && (errno == EAGAIN || errno == EWOULDBLOCK))
            return true;
        else
        {
            /*
             * Postmaster is dead, or something went wrong with the read()
             * call.
             */
 
#ifdef USE_POSTMASTER_DEATH_SIGNAL
            postmaster_possibly_dead = true;
#endif
 
            if (rc < 0)
                elog(FATAL, "read on postmaster death monitoring pipe failed: %m");
            else if (rc > 0)
                elog(FATAL, "unexpected data in postmaster death monitoring pipe");
 
            return false;
        }
    }
 
#else                           /* WIN32 */
    if (WaitForSingleObject(PostmasterHandle, 0) == WAIT_TIMEOUT)
        return true;
    else
    {
#ifdef USE_POSTMASTER_DEATH_SIGNAL
        postmaster_possibly_dead = true;
#endif
        return false;
    }
#endif                          /* WIN32 */
}

References EAGAIN, elog, EWOULDBLOCK, FATAL, postmaster_alive_fds, POSTMASTER_FD_WATCH, and read.

Referenced by WaitEventSetWaitBlock().

RegisterPostmasterChildActive()

void RegisterPostmasterChildActive

(

void

)

Definition at line 329 of file pmsignal.c.

{
    int         slot = MyPMChildSlot;
 
    Assert(slot > 0 && slot <= PMSignalState->num_child_flags);
    slot--;
    Assert(PMSignalState->PMChildFlags[slot] == PM_CHILD_ASSIGNED);
    PMSignalState->PMChildFlags[slot] = PM_CHILD_ACTIVE;
 
    /* Arrange to clean up at exit. */
    on_shmem_exit(MarkPostmasterChildInactive, 0);
}

References Assert, MarkPostmasterChildInactive(), MyPMChildSlot, on_shmem_exit(), PM_CHILD_ACTIVE, PM_CHILD_ASSIGNED, PMSignalData::PMChildFlags, and PMSignalState.

Referenced by InitProcess().

ReleasePostmasterChildSlot()

bool ReleasePostmasterChildSlot

(

int

slot

)

Definition at line 287 of file pmsignal.c.

{
    bool        result;
 
    Assert(slot > 0 && slot <= num_child_inuse);
    slot--;
 
    /*
     * Note: the slot state might already be unused, because the logic in
     * postmaster.c is such that this might get called twice when a child
     * crashes.  So we don't try to Assert anything about the state.
     */
    result = (PMSignalState->PMChildFlags[slot] == PM_CHILD_ASSIGNED);
    PMSignalState->PMChildFlags[slot] = PM_CHILD_UNUSED;
    PMChildInUse[slot] = false;
    return result;
}

References Assert, num_child_inuse, PM_CHILD_ASSIGNED, PM_CHILD_UNUSED, PMSignalData::PMChildFlags, PMChildInUse, and PMSignalState.

Referenced by BackendStartup(), CleanupBackend(), do_start_bgworker(), and StartAutovacuumWorker().

SendPostmasterSignal()

void SendPostmasterSignal

(

PMSignalReason

reason

)

Definition at line 184 of file pmsignal.c.

{
    /* If called in a standalone backend, do nothing */
    if (!IsUnderPostmaster)
        return;
    /* Atomically set the proper flag */
    PMSignalState->PMSignalFlags[reason] = true;
    /* Send signal to postmaster */
    kill(PostmasterPid, SIGUSR1);
}

References IsUnderPostmaster, kill, PMSignalData::PMSignalFlags, PMSignalState, PostmasterPid, and SIGUSR1.

Referenced by CheckRecoveryConsistency(), do_start_worker(), GetNewMultiXactId(), GetNewTransactionId(), PerformWalRecovery(), pg_rotate_logfile(), RegisterDynamicBackgroundWorker(), RequestXLogStreaming(), SetMultiXactIdLimit(), SetTransactionIdLimit(), and TerminateBackgroundWorker().

SetQuitSignalReason()

void SetQuitSignalReason

(

QuitSignalReason

reason

)

Definition at line 221 of file pmsignal.c.

{
    PMSignalState->sigquit_reason = reason;
}

References PMSignalState, and PMSignalData::sigquit_reason.

Referenced by HandleChildCrash(), and process_pm_shutdown_request().

Variable Documentation

next_child_inuse

int next_child_inuse

static

Definition at line 92 of file pmsignal.c.

Referenced by AssignPostmasterChildSlot(), and PMSignalShmemInit().

num_child_inuse

int num_child_inuse

static

Definition at line 91 of file pmsignal.c.

Referenced by AssignPostmasterChildSlot(), IsPostmasterChildWalSender(), PMSignalShmemInit(), and ReleasePostmasterChildSlot().

PMChildInUse

bool* PMChildInUse

static

Definition at line 93 of file pmsignal.c.

Referenced by AssignPostmasterChildSlot(), PMSignalShmemInit(), and ReleasePostmasterChildSlot().

PMSignalState

NON_EXEC_STATIC volatile PMSignalData* PMSignalState = NULL

Definition at line 84 of file pmsignal.c.

Referenced by AssignPostmasterChildSlot(), CheckPostmasterSignal(), GetQuitSignalReason(), IsPostmasterChildWalSender(), MarkPostmasterChildInactive(), MarkPostmasterChildWalSender(), PMSignalShmemInit(), RegisterPostmasterChildActive(), ReleasePostmasterChildSlot(), SendPostmasterSignal(), and SetQuitSignalReason().