gxact->proc.databaseId = databaseid;
gxact->proc.roleId = owner;
gxact->proc.inCommit = false;
+ MemSet(gxact->proc.signalFlags, 0, NUM_PROCSIGNALS * sizeof(sig_atomic_t));
gxact->proc.vacuumFlags = 0;
gxact->proc.lwWaiting = false;
gxact->proc.lwExclusive = false;
* a frontend command. Signal handler execution of inbound notifies
* is disabled until the next EnableNotifyInterrupt call.
*
- * The SIGUSR1 signal handler also needs to call this, so as to
- * prevent conflicts if one signal interrupts the other. So we
- * must return the previous state of the flag.
+ * This also needs to be called when SIGUSR1 with
+ * PROCSIG_CATCHUP_INTERRUPT is received, so as to prevent conflicts
+ * if one signal interrupts the other. So we must return the previous
+ * state of the flag.
*/
bool
DisableNotifyInterrupt(void)
nulls[Natts_pg_listener];
bool catchup_enabled;
- /* Must prevent SIGUSR1 interrupt while I am running */
+ /* Must prevent catchup interrupt while I am running */
catchup_enabled = DisableCatchupInterrupt();
if (Trace_notify)
pqsignal(SIGALRM, handle_sig_alarm);
pqsignal(SIGPIPE, SIG_IGN);
- pqsignal(SIGUSR1, CatchupInterruptHandler);
+ pqsignal(SIGUSR1, proc_sigusr1_handler);
/* We don't listen for async notifies */
pqsignal(SIGUSR2, SIG_IGN);
pqsignal(SIGFPE, FloatExceptionHandler);
* Because backends sitting idle will not be reading sinval events, we
* need a way to give an idle backend a swift kick in the rear and make
* it catch up before the sinval queue overflows and forces it to go
- * through a cache reset exercise. This is done by sending SIGUSR1
- * to any backend that gets too far behind.
+ * through a cache reset exercise. This is done by sending
+ * PROCSIG_CATCHUP_INTERRUPT to any backend that gets too far behind.
*
* State for catchup events consists of two flags: one saying whether
* the signal handler is currently allowed to call ProcessCatchupEvent
/*
- * CatchupInterruptHandler
+ * HandleCatchupInterrupt
*
- * This is the signal handler for SIGUSR1.
+ * This is called when PROCSIG_CATCHUP_INTERRUPT signal is received.
*
* If we are idle (catchupInterruptEnabled is set), we can safely
* invoke ProcessCatchupEvent directly. Otherwise, just set a flag
* since there's no longer any reason to do anything.)
*/
void
-CatchupInterruptHandler(SIGNAL_ARGS)
+HandleCatchupInterrupt(void)
{
- int save_errno = errno;
-
/*
- * Note: this is a SIGNAL HANDLER. You must be very wary what you do
- * here.
+ * Note: this is called by a SIGNAL HANDLER.
+ * You must be very wary what you do here.
*/
/* Don't joggle the elbow of proc_exit */
*/
catchupInterruptOccurred = 1;
}
-
- errno = save_errno;
}
/*
/*
* ProcessCatchupEvent
*
- * Respond to a catchup event (SIGUSR1) from another backend.
+ * Respond to a catchup event (PROCSIG_CATCHUP_INTERRUPT) from another
+ * backend.
*
* This is called either directly from the SIGUSR1 signal handler,
* or the next time control reaches the outer idle loop (assuming
#include "storage/backendid.h"
#include "storage/ipc.h"
#include "storage/proc.h"
+#include "storage/procarray.h"
#include "storage/shmem.h"
#include "storage/sinvaladt.h"
#include "storage/spin.h"
/* Per-backend state in shared invalidation structure */
typedef struct ProcState
{
- /* procPid is zero in an inactive ProcState array entry. */
- pid_t procPid; /* PID of backend, for signaling */
- /* nextMsgNum is meaningless if procPid == 0 or resetState is true. */
+ /* proc is NULL in an inactive ProcState array entry. */
+ PGPROC *proc; /* PGPROC entry of backend, for signaling */
+ /* nextMsgNum is meaningless if proc == NULL or resetState is true. */
int nextMsgNum; /* next message number to read */
bool resetState; /* backend needs to reset its state */
bool signaled; /* backend has been sent catchup signal */
/* Mark all backends inactive, and initialize nextLXID */
for (i = 0; i < shmInvalBuffer->maxBackends; i++)
{
- shmInvalBuffer->procState[i].procPid = 0; /* inactive */
+ shmInvalBuffer->procState[i].proc = NULL; /* inactive */
shmInvalBuffer->procState[i].nextMsgNum = 0; /* meaningless */
shmInvalBuffer->procState[i].resetState = false;
shmInvalBuffer->procState[i].signaled = false;
/* Look for a free entry in the procState array */
for (index = 0; index < segP->lastBackend; index++)
{
- if (segP->procState[index].procPid == 0) /* inactive slot? */
+ if (segP->procState[index].proc == NULL) /* inactive slot? */
{
stateP = &segP->procState[index];
break;
if (segP->lastBackend < segP->maxBackends)
{
stateP = &segP->procState[segP->lastBackend];
- Assert(stateP->procPid == 0);
+ Assert(stateP->proc == NULL);
segP->lastBackend++;
}
else
nextLocalTransactionId = stateP->nextLXID;
/* mark myself active, with all extant messages already read */
- stateP->procPid = MyProcPid;
+ stateP->proc = MyProc;
stateP->nextMsgNum = segP->maxMsgNum;
stateP->resetState = false;
stateP->signaled = false;
stateP->nextLXID = nextLocalTransactionId;
/* Mark myself inactive */
- stateP->procPid = 0;
+ stateP->proc = NULL;
stateP->nextMsgNum = 0;
stateP->resetState = false;
stateP->signaled = false;
/* Recompute index of last active backend */
for (i = segP->lastBackend; i > 0; i--)
{
- if (segP->procState[i - 1].procPid != 0)
+ if (segP->procState[i - 1].proc != NULL)
break;
}
segP->lastBackend = i;
{
ProcState *stateP = &segP->procState[backendID - 1];
- result = (stateP->procPid != 0);
+ result = (stateP->proc != NULL);
}
else
result = false;
int n = stateP->nextMsgNum;
/* Ignore if inactive or already in reset state */
- if (stateP->procPid == 0 || stateP->resetState)
+ if (stateP->proc == NULL || stateP->resetState)
continue;
/*
segP->nextThreshold = (numMsgs / CLEANUP_QUANTUM + 1) * CLEANUP_QUANTUM;
/*
- * Lastly, signal anyone who needs a catchup interrupt. Since kill()
- * might not be fast, we don't want to hold locks while executing it.
+ * Lastly, signal anyone who needs a catchup interrupt. Since
+ * SendProcSignal() might not be fast, we don't want to hold locks while
+ * executing it.
*/
if (needSig)
{
- pid_t his_pid = needSig->procPid;
+ PGPROC *his_proc = needSig->proc;
needSig->signaled = true;
LWLockRelease(SInvalReadLock);
LWLockRelease(SInvalWriteLock);
- elog(DEBUG4, "sending sinval catchup signal to PID %d", (int) his_pid);
- kill(his_pid, SIGUSR1);
+ elog(DEBUG4, "sending sinval catchup signal to PID %d",
+ (int) his_proc->pid);
+ SendProcSignal(his_proc, PROCSIG_CATCHUP_INTERRUPT);
if (callerHasWriteLock)
LWLockAcquire(SInvalWriteLock, LW_EXCLUSIVE);
}
MyProc->databaseId = InvalidOid;
MyProc->roleId = InvalidOid;
MyProc->inCommit = false;
+ MemSet(MyProc->signalFlags, 0, NUM_PROCSIGNALS * sizeof(sig_atomic_t));
MyProc->vacuumFlags = 0;
if (IsAutoVacuumWorkerProcess())
MyProc->vacuumFlags |= PROC_IS_AUTOVACUUM;
MyProc->databaseId = InvalidOid;
MyProc->roleId = InvalidOid;
MyProc->inCommit = false;
+ MemSet(MyProc->signalFlags, 0, NUM_PROCSIGNALS * sizeof(sig_atomic_t));
/* we don't set the "is autovacuum" flag in the launcher */
MyProc->vacuumFlags = 0;
MyProc->lwWaiting = false;
PGSemaphoreUnlock(&proc->sem);
}
+/*
+ * SendProcSignal - send the signal with the reason to a process.
+ *
+ * The process can be a backend or an auxiliary process that has a PGPROC
+ * entry, like an autovacuum worker.
+ */
+void
+SendProcSignal(PGPROC *proc, ProcSignalReason reason)
+{
+ pid_t pid;
+
+ /*
+ * If the process is gone, do nothing.
+ *
+ * Since there's no locking, it's possible that the process detaches
+ * from shared memory and exits right after this test, before we set
+ * the flag and send signal. And the PGPROC entry might even be recycled
+ * by a new process, so it's remotely possible that we signal a wrong
+ * process. That's OK, all the signals are such that no harm is done.
+ */
+ pid = proc->pid;
+ if (pid == 0)
+ return;
+
+ /* Atomically set the proper flag */
+ proc->signalFlags[reason] = true;
+ /* Send SIGUSR1 to the process */
+ kill(pid, SIGUSR1);
+}
+
+/*
+ * CheckProcSignal - check to see if the particular reason has been
+ * signaled, and clear the signal flag. Should be called after
+ * receiving SIGUSR1.
+ */
+bool
+CheckProcSignal(ProcSignalReason reason)
+{
+ /* Careful here --- don't clear flag if we haven't seen it set */
+ if (MyProc->signalFlags[reason])
+ {
+ MyProc->signalFlags[reason] = false;
+ return true;
+ }
+
+ return false;
+}
+
/*****************************************************************************
* SIGALRM interrupt support
* --------------------------------
*/
+/*
+ * proc_sigusr1_handler - handle SIGUSR1 signal.
+ *
+ * SIGUSR1 is multiplexed to handle multiple different events. The signalFlags
+ * array in PGPROC indicates which events have been signaled.
+ */
+void
+proc_sigusr1_handler(SIGNAL_ARGS)
+{
+ int save_errno = errno;
+
+ if (CheckProcSignal(PROCSIG_CATCHUP_INTERRUPT))
+ HandleCatchupInterrupt();
+
+ errno = save_errno;
+}
+
/*
* quickdie() occurs when signalled SIGQUIT by the postmaster.
*
* of output during who-knows-what operation...
*/
pqsignal(SIGPIPE, SIG_IGN);
- pqsignal(SIGUSR1, CatchupInterruptHandler);
+ pqsignal(SIGUSR1, proc_sigusr1_handler);
pqsignal(SIGUSR2, NotifyInterruptHandler);
pqsignal(SIGFPE, FloatExceptionHandler);
#ifndef _PROC_H_
#define _PROC_H_
+#include <signal.h>
+
#include "storage/lock.h"
#include "storage/pg_sema.h"
TransactionId xids[PGPROC_MAX_CACHED_SUBXIDS];
};
+/*
+ * Reasons for signaling a process (a backend or an auxiliary process, like
+ * autovacuum worker). We can cope with simultaneous signals for different
+ * reasons. If the same reason is signaled multiple times in quick succession,
+ * however, the process is likely to observe only one notification of it.
+ * This is okay for the present uses.
+ */
+typedef enum
+{
+ PROCSIG_CATCHUP_INTERRUPT, /* catchup interrupt */
+ NUM_PROCSIGNALS /* Must be last value of enum! */
+} ProcSignalReason;
+
/* Flags for PGPROC->vacuumFlags */
#define PROC_IS_AUTOVACUUM 0x01 /* is it an autovac worker? */
#define PROC_IN_VACUUM 0x02 /* currently running lazy vacuum */
uint8 vacuumFlags; /* vacuum-related flags, see above */
+ /*
+ * SIGUSR1 signal is multiplexed for multiple purposes. signalFlags
+ * indicates which "reasons" have been signaled.
+ *
+ * The flags are declared as "volatile sig_atomic_t" for maximum
+ * portability. This should ensure that loads and stores of the flag
+ * values are atomic, allowing us to dispense with any explicit locking.
+ */
+ volatile sig_atomic_t signalFlags[NUM_PROCSIGNALS];
+
/* Info about LWLock the process is currently waiting for, if any. */
bool lwWaiting; /* true if waiting for an LW lock */
bool lwExclusive; /* true if waiting for exclusive access */
extern void ProcWaitForSignal(void);
extern void ProcSendSignal(int pid);
+extern void SendProcSignal(PGPROC *proc, ProcSignalReason reason);
+extern bool CheckProcSignal(ProcSignalReason reason);
+
extern bool enable_sig_alarm(int delayms, bool is_statement_timeout);
extern bool disable_sig_alarm(bool is_statement_timeout);
extern void handle_sig_alarm(SIGNAL_ARGS);
void (*resetFunction) (void));
/* signal handler for catchup events (SIGUSR1) */
-extern void CatchupInterruptHandler(SIGNAL_ARGS);
+extern void HandleCatchupInterrupt(void);
/*
* enable/disable processing of catchup events directly from signal handler.
extern bool assign_max_stack_depth(int newval, bool doit, GucSource source);
+extern void proc_sigusr1_handler(SIGNAL_ARGS);
extern void die(SIGNAL_ARGS);
extern void quickdie(SIGNAL_ARGS);
extern void authdie(SIGNAL_ARGS);
projects / users / simon / postgres.git / commitdiff