signalfuncs.c File Reference

#include "postgres.h"
#include <signal.h>
#include "catalog/pg_authid.h"
#include "miscadmin.h"
#include "pgstat.h"
#include "postmaster/syslogger.h"
#include "storage/pmsignal.h"
#include "storage/proc.h"
#include "storage/procarray.h"
#include "utils/acl.h"
#include "utils/fmgrprotos.h"

Include dependency graph for signalfuncs.c:

Go to the source code of this file.

Macros
#define	SIGNAL_BACKEND_SUCCESS   0
#define	SIGNAL_BACKEND_ERROR   1
#define	SIGNAL_BACKEND_NOPERMISSION   2
#define	SIGNAL_BACKEND_NOSUPERUSER   3
#define	SIGNAL_BACKEND_NOAUTOVAC   4

Functions
static int	pg_signal_backend (int pid, int sig)
Datum	pg_cancel_backend (PG_FUNCTION_ARGS)
static bool	pg_wait_until_termination (int pid, int64 timeout)
Datum	pg_terminate_backend (PG_FUNCTION_ARGS)
Datum	pg_reload_conf (PG_FUNCTION_ARGS)
Datum	pg_rotate_logfile (PG_FUNCTION_ARGS)

Macro Definition Documentation

SIGNAL_BACKEND_ERROR

#define SIGNAL_BACKEND_ERROR   1

Definition at line 46 of file signalfuncs.c.

SIGNAL_BACKEND_NOAUTOVAC

#define SIGNAL_BACKEND_NOAUTOVAC   4

Definition at line 49 of file signalfuncs.c.

SIGNAL_BACKEND_NOPERMISSION

#define SIGNAL_BACKEND_NOPERMISSION   2

Definition at line 47 of file signalfuncs.c.

SIGNAL_BACKEND_NOSUPERUSER

#define SIGNAL_BACKEND_NOSUPERUSER   3

Definition at line 48 of file signalfuncs.c.

SIGNAL_BACKEND_SUCCESS

#define SIGNAL_BACKEND_SUCCESS   0

Definition at line 45 of file signalfuncs.c.

Function Documentation

pg_cancel_backend()

Datum pg_cancel_backend

(

PG_FUNCTION_ARGS

)

Definition at line 136 of file signalfuncs.c.

{
    int         r = pg_signal_backend(PG_GETARG_INT32(0), SIGINT);
 
    if (r == SIGNAL_BACKEND_NOSUPERUSER)
        ereport(ERROR,
                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                 errmsg("permission denied to cancel query"),
                 errdetail("Only roles with the %s attribute may cancel queries of roles with the %s attribute.",
                           "SUPERUSER", "SUPERUSER")));
 
    if (r == SIGNAL_BACKEND_NOAUTOVAC)
        ereport(ERROR,
                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                 errmsg("permission denied to cancel query"),
                 errdetail("Only roles with privileges of the \"%s\" role may cancel autovacuum workers.",
                           "pg_signal_autovacuum_worker")));
 
    if (r == SIGNAL_BACKEND_NOPERMISSION)
        ereport(ERROR,
                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                 errmsg("permission denied to cancel query"),
                 errdetail("Only roles with privileges of the role whose query is being canceled or with privileges of the \"%s\" role may cancel this query.",
                           "pg_signal_backend")));
 
    PG_RETURN_BOOL(r == SIGNAL_BACKEND_SUCCESS);
}

References ereport, errcode(), errdetail(), errmsg(), ERROR, PG_GETARG_INT32, PG_RETURN_BOOL, pg_signal_backend(), SIGNAL_BACKEND_NOAUTOVAC, SIGNAL_BACKEND_NOPERMISSION, SIGNAL_BACKEND_NOSUPERUSER, and SIGNAL_BACKEND_SUCCESS.

pg_reload_conf()

Datum pg_reload_conf

(

PG_FUNCTION_ARGS

)

Definition at line 288 of file signalfuncs.c.

{
    if (kill(PostmasterPid, SIGHUP))
    {
        ereport(WARNING,
                (errmsg("failed to send signal to postmaster: %m")));
        PG_RETURN_BOOL(false);
    }
 
    PG_RETURN_BOOL(true);
}

References ereport, errmsg(), kill, PG_RETURN_BOOL, PostmasterPid, SIGHUP, and WARNING.

pg_rotate_logfile()

Datum pg_rotate_logfile

(

PG_FUNCTION_ARGS

)

Definition at line 308 of file signalfuncs.c.

{
    if (!Logging_collector)
    {
        ereport(WARNING,
                (errmsg("rotation not possible because log collection not active")));
        PG_RETURN_BOOL(false);
    }
 
    SendPostmasterSignal(PMSIGNAL_ROTATE_LOGFILE);
    PG_RETURN_BOOL(true);
}

References ereport, errmsg(), Logging_collector, PG_RETURN_BOOL, PMSIGNAL_ROTATE_LOGFILE, SendPostmasterSignal(), and WARNING.

pg_signal_backend()

static int pg_signal_backend ( int  pid, int  sig  )

static

Definition at line 51 of file signalfuncs.c.

{
    PGPROC     *proc = BackendPidGetProc(pid);
 
    /*
     * BackendPidGetProc returns NULL if the pid isn't valid; but by the time
     * we reach kill(), a process for which we get a valid proc here might
     * have terminated on its own.  There's no way to acquire a lock on an
     * arbitrary process to prevent that. But since so far all the callers of
     * this mechanism involve some request for ending the process anyway, that
     * it might end on its own first is not a problem.
     *
     * Note that proc will also be NULL if the pid refers to an auxiliary
     * process or the postmaster (neither of which can be signaled via
     * pg_signal_backend()).
     */
    if (proc == NULL)
    {
        /*
         * This is just a warning so a loop-through-resultset will not abort
         * if one backend terminated on its own during the run.
         */
        ereport(WARNING,
                (errmsg("PID %d is not a PostgreSQL backend process", pid)));
 
        return SIGNAL_BACKEND_ERROR;
    }
 
    /*
     * Only allow superusers to signal superuser-owned backends.  Any process
     * not advertising a role might have the importance of a superuser-owned
     * backend, so treat it that way.  As an exception, we allow roles with
     * privileges of pg_signal_autovacuum_worker to signal autovacuum workers
     * (which do not advertise a role).
     *
     * Otherwise, users can signal backends for roles they have privileges of.
     */
    if (!OidIsValid(proc->roleId) || superuser_arg(proc->roleId))
    {
        ProcNumber  procNumber = GetNumberFromPGProc(proc);
        PgBackendStatus *procStatus = pgstat_get_beentry_by_proc_number(procNumber);
 
        if (procStatus && procStatus->st_backendType == B_AUTOVAC_WORKER)
        {
            if (!has_privs_of_role(GetUserId(), ROLE_PG_SIGNAL_AUTOVACUUM_WORKER))
                return SIGNAL_BACKEND_NOAUTOVAC;
        }
        else if (!superuser())
            return SIGNAL_BACKEND_NOSUPERUSER;
    }
    else if (!has_privs_of_role(GetUserId(), proc->roleId) &&
             !has_privs_of_role(GetUserId(), ROLE_PG_SIGNAL_BACKEND))
        return SIGNAL_BACKEND_NOPERMISSION;
 
    /*
     * Can the process we just validated above end, followed by the pid being
     * recycled for a new process, before reaching here?  Then we'd be trying
     * to kill the wrong thing.  Seems near impossible when sequential pid
     * assignment and wraparound is used.  Perhaps it could happen on a system
     * where pid re-use is randomized.  That race condition possibility seems
     * too unlikely to worry about.
     */
 
    /* If we have setsid(), signal the backend's whole process group */
#ifdef HAVE_SETSID
    if (kill(-pid, sig))
#else
    if (kill(pid, sig))
#endif
    {
        /* Again, just a warning to allow loops */
        ereport(WARNING,
                (errmsg("could not send signal to process %d: %m", pid)));
        return SIGNAL_BACKEND_ERROR;
    }
    return SIGNAL_BACKEND_SUCCESS;
}

References B_AUTOVAC_WORKER, BackendPidGetProc(), ereport, errmsg(), GetNumberFromPGProc, GetUserId(), has_privs_of_role(), kill, OidIsValid, pgstat_get_beentry_by_proc_number(), PGPROC::roleId, sig, SIGNAL_BACKEND_ERROR, SIGNAL_BACKEND_NOAUTOVAC, SIGNAL_BACKEND_NOPERMISSION, SIGNAL_BACKEND_NOSUPERUSER, SIGNAL_BACKEND_SUCCESS, PgBackendStatus::st_backendType, superuser(), superuser_arg(), and WARNING.

Referenced by pg_cancel_backend(), and pg_terminate_backend().

pg_terminate_backend()

Datum pg_terminate_backend

(

PG_FUNCTION_ARGS

)

Definition at line 237 of file signalfuncs.c.

{
    int         pid;
    int         r;
    int         timeout;        /* milliseconds */
 
    pid = PG_GETARG_INT32(0);
    timeout = PG_GETARG_INT64(1);
 
    if (timeout < 0)
        ereport(ERROR,
                (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                 errmsg("\"timeout\" must not be negative")));
 
    r = pg_signal_backend(pid, SIGTERM);
 
    if (r == SIGNAL_BACKEND_NOSUPERUSER)
        ereport(ERROR,
                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                 errmsg("permission denied to terminate process"),
                 errdetail("Only roles with the %s attribute may terminate processes of roles with the %s attribute.",
                           "SUPERUSER", "SUPERUSER")));
 
    if (r == SIGNAL_BACKEND_NOAUTOVAC)
        ereport(ERROR,
                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                 errmsg("permission denied to terminate process"),
                 errdetail("Only roles with privileges of the \"%s\" role may terminate autovacuum workers.",
                           "pg_signal_autovacuum_worker")));
 
    if (r == SIGNAL_BACKEND_NOPERMISSION)
        ereport(ERROR,
                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                 errmsg("permission denied to terminate process"),
                 errdetail("Only roles with privileges of the role whose process is being terminated or with privileges of the \"%s\" role may terminate this process.",
                           "pg_signal_backend")));
 
    /* Wait only on success and if actually requested */
    if (r == SIGNAL_BACKEND_SUCCESS && timeout > 0)
        PG_RETURN_BOOL(pg_wait_until_termination(pid, timeout));
    else
        PG_RETURN_BOOL(r == SIGNAL_BACKEND_SUCCESS);
}

References ereport, errcode(), errdetail(), errmsg(), ERROR, PG_GETARG_INT32, PG_GETARG_INT64, PG_RETURN_BOOL, pg_signal_backend(), pg_wait_until_termination(), SIGNAL_BACKEND_NOAUTOVAC, SIGNAL_BACKEND_NOPERMISSION, SIGNAL_BACKEND_NOSUPERUSER, and SIGNAL_BACKEND_SUCCESS.

pg_wait_until_termination()

static bool pg_wait_until_termination ( int  pid, int64  timeout  )

static

Definition at line 169 of file signalfuncs.c.

{
    /*
     * Wait in steps of waittime milliseconds until this function exits or
     * timeout.
     */
    int64       waittime = 100;
 
    /*
     * Initially remaining time is the entire timeout specified by the user.
     */
    int64       remainingtime = timeout;
 
    /*
     * Check existence of the backend. If the backend still exists, then wait
     * for waittime milliseconds, again check for the existence. Repeat this
     * until timeout or an error occurs or a pending interrupt such as query
     * cancel gets processed.
     */
    do
    {
        if (remainingtime < waittime)
            waittime = remainingtime;
 
        if (kill(pid, 0) == -1)
        {
            if (errno == ESRCH)
                return true;
            else
                ereport(ERROR,
                        (errcode(ERRCODE_INTERNAL_ERROR),
                         errmsg("could not check the existence of the backend with PID %d: %m",
                                pid)));
        }
 
        /* Process interrupts, if any, before waiting */
        CHECK_FOR_INTERRUPTS();
 
        (void) WaitLatch(MyLatch,
                         WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
                         waittime,
                         WAIT_EVENT_BACKEND_TERMINATION);
 
        ResetLatch(MyLatch);
 
        remainingtime -= waittime;
    } while (remainingtime > 0);
 
    ereport(WARNING,
            (errmsg_plural("backend with PID %d did not terminate within %lld millisecond",
                           "backend with PID %d did not terminate within %lld milliseconds",
                           timeout,
                           pid, (long long int) timeout)));
 
    return false;
}

References CHECK_FOR_INTERRUPTS, ereport, errcode(), errmsg(), errmsg_plural(), ERROR, kill, MyLatch, ResetLatch(), WaitLatch(), WARNING, WL_EXIT_ON_PM_DEATH, WL_LATCH_SET, and WL_TIMEOUT.

Referenced by pg_terminate_backend().