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Postgres FD Implementation
Commit 6e072287 authored by Tom Lane's avatar Tom Lane
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Code review for log_lock_waits patch. Don't try to issue log messages from 

within a signal handler (this might be safe given the relatively narrow code
range in which the interrupt is enabled, but it seems awfully risky); do issue
more informative log messages that tell what is being waited for and the exact
length of the wait; minor other code cleanup.  Greg Stark and Tom Lane
parent 4c310eca
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Showing with 229 additions and 155 deletions
doc/src/sgml/config.sgml
View file @ 6e072287
<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.126 2007/06/07 19:19:56 tgl Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.127 2007/06/19 20:13:21 tgl Exp $ -->
<chapter Id="runtime-config">
<title>Server Configuration</title>
......@@ -2947,7 +2947,7 @@ SELECT * FROM parent WHERE key = 2400;
</indexterm>
<listitem>
<para>
Controls whether a log message is produced when a statement waits
Controls whether a log message is produced when a session waits
longer than <xref linkend="guc-deadlock-timeout"> to acquire a
lock. This is useful in determining if lock waits are causing
poor performance. The default is <literal>off</>.
......@@ -4084,11 +4084,18 @@ dynamic_library_path = 'C:\tools\postgresql;H:\my_project\lib;$libdir'
wasted in needless deadlock checks, but slows down reporting of
real deadlock errors. The default is one second (<literal>1s</>),
which is probably about the smallest value you would want in
practice. Set <xref linkend="guc-log-lock-waits"> to log deadlock
checks. On a heavily loaded server you might want to raise it.
practice. On a heavily loaded server you might want to raise it.
Ideally the setting should exceed your typical transaction time,
so as to improve the odds that a lock will be released before the
waiter decides to check for deadlock.
so as to improve the odds that a lock will be released before
the waiter decides to check for deadlock.
</para>
<para>
When <xref linkend="guc-log-lock-waits"> is set,
this parameter also determines the length of time to wait before
a log message is issued about the lock wait. If you are trying
to investigate locking delays you might want to set a shorter than
normal <varname>deadlock_timeout</varname>.
</para>
</listitem>
</varlistentry>
......
src/backend/storage/lmgr/deadlock.c
View file @ 6e072287
......@@ -12,7 +12,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/lmgr/deadlock.c,v 1.47 2007/04/20 20:15:52 momjian Exp $
* $PostgreSQL: pgsql/src/backend/storage/lmgr/deadlock.c,v 1.48 2007/06/19 20:13:21 tgl Exp $
*
* Interface:
*
......@@ -25,8 +25,8 @@
*/
#include "postgres.h"
#include "lib/stringinfo.h"
#include "miscadmin.h"
#include "storage/lmgr.h"
#include "storage/proc.h"
#include "utils/memutils.h"
......@@ -117,8 +117,9 @@ static int nDeadlockDetails;
* allocation of working memory for DeadLockCheck. We do this per-backend
* since there's no percentage in making the kernel do copy-on-write
* inheritance of workspace from the postmaster. We want to allocate the
* space at startup because the deadlock checker might be invoked when there's
* no free memory left.
* space at startup because (a) the deadlock checker might be invoked when
* there's no free memory left, and (b) the checker is normally run inside a
* signal handler, which is a very dangerous place to invoke palloc from.
*/
void
InitDeadLockChecking(void)
......@@ -184,17 +185,17 @@ InitDeadLockChecking(void)
*
* This code looks for deadlocks involving the given process. If any
* are found, it tries to rearrange lock wait queues to resolve the
* deadlock. If resolution is impossible, return TRUE --- the caller
* is then expected to abort the given proc's transaction.
* deadlock. If resolution is impossible, return DS_HARD_DEADLOCK ---
* the caller is then expected to abort the given proc's transaction.
*
* Caller must already have locked all partitions of the lock tables,
* so standard error logging/reporting code is handled by caller.
* Caller must already have locked all partitions of the lock tables.
*
* On failure, deadlock details are recorded in deadlockDetails[] for
* subsequent printing by DeadLockReport(). That activity is separate
* because we don't want to do it while holding all those LWLocks.
* because (a) we don't want to do it while holding all those LWLocks,
* and (b) we are typically invoked inside a signal handler.
*/
DeadlockState
DeadLockState
DeadLockCheck(PGPROC *proc)
{
int i,
......@@ -205,11 +206,6 @@ DeadLockCheck(PGPROC *proc)
nPossibleConstraints = 0;
nWaitOrders = 0;
#ifdef LOCK_DEBUG
if (Debug_deadlocks)
DumpAllLocks();
#endif
/* Search for deadlocks and possible fixes */
if (DeadLockCheckRecurse(proc))
{
......@@ -256,10 +252,11 @@ DeadLockCheck(PGPROC *proc)
ProcLockWakeup(GetLocksMethodTable(lock), lock);
}
/* Return code tells caller if we had to escape a deadlock or not */
if (nWaitOrders > 0)
return DS_SOFT_DEADLOCK;
else
return DS_DEADLOCK_NOT_FOUND;
return DS_NO_DEADLOCK;
}
/*
......@@ -833,82 +830,7 @@ PrintLockQueue(LOCK *lock, const char *info)
#endif
/*
* Append a description of a lockable object to buf.
*
* XXX probably this should be exported from lmgr.c or some such place.
* Ideally we would print names for the numeric values, but that requires
* getting locks on system tables, which might cause problems.
*/
static void
DescribeLockTag(StringInfo buf, const LOCKTAG *lock)
{
switch (lock->locktag_type)
{
case LOCKTAG_RELATION:
appendStringInfo(buf,
_("relation %u of database %u"),
lock->locktag_field2,
lock->locktag_field1);
break;
case LOCKTAG_RELATION_EXTEND:
appendStringInfo(buf,
_("extension of relation %u of database %u"),
lock->locktag_field2,
lock->locktag_field1);
break;
case LOCKTAG_PAGE:
appendStringInfo(buf,
_("page %u of relation %u of database %u"),
lock->locktag_field3,
lock->locktag_field2,
lock->locktag_field1);
break;
case LOCKTAG_TUPLE:
appendStringInfo(buf,
_("tuple (%u,%u) of relation %u of database %u"),
lock->locktag_field3,
lock->locktag_field4,
lock->locktag_field2,
lock->locktag_field1);
break;
case LOCKTAG_TRANSACTION:
appendStringInfo(buf,
_("transaction %u"),
lock->locktag_field1);
break;
case LOCKTAG_OBJECT:
appendStringInfo(buf,
_("object %u of class %u of database %u"),
lock->locktag_field3,
lock->locktag_field2,
lock->locktag_field1);
break;
case LOCKTAG_USERLOCK:
/* reserved for old contrib code, now on pgfoundry */
appendStringInfo(buf,
_("user lock [%u,%u,%u]"),
lock->locktag_field1,
lock->locktag_field2,
lock->locktag_field3);
break;
case LOCKTAG_ADVISORY:
appendStringInfo(buf,
_("advisory lock [%u,%u,%u,%u]"),
lock->locktag_field1,
lock->locktag_field2,
lock->locktag_field3,
lock->locktag_field4);
break;
default:
appendStringInfo(buf,
_("unrecognized locktag type %d"),
lock->locktag_type);
break;
}
}
/*
* Report a detected DS_HARD_DEADLOCK, with available details.
* Report a detected deadlock, with available details.
*/
void
DeadLockReport(void)
......
src/backend/storage/lmgr/lmgr.c
View file @ 6e072287
......@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/lmgr/lmgr.c,v 1.90 2007/01/05 22:19:38 momjian Exp $
* $PostgreSQL: pgsql/src/backend/storage/lmgr/lmgr.c,v 1.91 2007/06/19 20:13:21 tgl Exp $
*
*-------------------------------------------------------------------------
*/
......@@ -635,3 +635,79 @@ LockTagIsTemp(const LOCKTAG *tag)
}
return false; /* default case */
}
/*
* Append a description of a lockable object to buf.
*
* Ideally we would print names for the numeric values, but that requires
* getting locks on system tables, which might cause problems since this is
* typically used to report deadlock situations.
*/
void
DescribeLockTag(StringInfo buf, const LOCKTAG *tag)
{
switch (tag->locktag_type)
{
case LOCKTAG_RELATION:
appendStringInfo(buf,
_("relation %u of database %u"),
tag->locktag_field2,
tag->locktag_field1);
break;
case LOCKTAG_RELATION_EXTEND:
appendStringInfo(buf,
_("extension of relation %u of database %u"),
tag->locktag_field2,
tag->locktag_field1);
break;
case LOCKTAG_PAGE:
appendStringInfo(buf,
_("page %u of relation %u of database %u"),
tag->locktag_field3,
tag->locktag_field2,
tag->locktag_field1);
break;
case LOCKTAG_TUPLE:
appendStringInfo(buf,
_("tuple (%u,%u) of relation %u of database %u"),
tag->locktag_field3,
tag->locktag_field4,
tag->locktag_field2,
tag->locktag_field1);
break;
case LOCKTAG_TRANSACTION:
appendStringInfo(buf,
_("transaction %u"),
tag->locktag_field1);
break;
case LOCKTAG_OBJECT:
appendStringInfo(buf,
_("object %u of class %u of database %u"),
tag->locktag_field3,
tag->locktag_field2,
tag->locktag_field1);
break;
case LOCKTAG_USERLOCK:
/* reserved for old contrib code, now on pgfoundry */
appendStringInfo(buf,
_("user lock [%u,%u,%u]"),
tag->locktag_field1,
tag->locktag_field2,
tag->locktag_field3);
break;
case LOCKTAG_ADVISORY:
appendStringInfo(buf,
_("advisory lock [%u,%u,%u,%u]"),
tag->locktag_field1,
tag->locktag_field2,
tag->locktag_field3,
tag->locktag_field4);
break;
default:
appendStringInfo(buf,
_("unrecognized locktag type %d"),
tag->locktag_type);
break;
}
}
src/backend/storage/lmgr/proc.c
View file @ 6e072287
......@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/lmgr/proc.c,v 1.188 2007/04/16 18:29:53 alvherre Exp $
* $PostgreSQL: pgsql/src/backend/storage/lmgr/proc.c,v 1.189 2007/06/19 20:13:21 tgl Exp $
*
*-------------------------------------------------------------------------
*/
......@@ -40,6 +40,7 @@
#include "miscadmin.h"
#include "postmaster/autovacuum.h"
#include "storage/ipc.h"
#include "storage/lmgr.h"
#include "storage/proc.h"
#include "storage/procarray.h"
#include "storage/spin.h"
......@@ -72,8 +73,12 @@ static LOCALLOCK *lockAwaited = NULL;
/* Mark these volatile because they can be changed by signal handler */
static volatile bool statement_timeout_active = false;
static volatile bool deadlock_timeout_active = false;
static volatile DeadLockState deadlock_state = DS_NOT_YET_CHECKED;
volatile bool cancel_from_timeout = false;
/* timeout_start_time is set when log_lock_waits is true */
static TimestampTz timeout_start_time;
/* statement_fin_time is valid only if statement_timeout_active is true */
static TimestampTz statement_fin_time;
......@@ -837,6 +842,9 @@ ProcSleep(LOCALLOCK *locallock, LockMethod lockMethodTable)
*/
LWLockRelease(partitionLock);
/* Reset deadlock_state before enabling the signal handler */
deadlock_state = DS_NOT_YET_CHECKED;
/*
* Set timer so we can wake up after awhile and check for a deadlock. If a
* deadlock is detected, the handler releases the process's semaphore and
......@@ -869,6 +877,60 @@ ProcSleep(LOCALLOCK *locallock, LockMethod lockMethodTable)
do
{
PGSemaphoreLock(&MyProc->sem, true);
/*
* If awoken after the deadlock check interrupt has run, and
* log_lock_waits is on, then report about the wait.
*/
if (log_lock_waits)
{
switch (deadlock_state)
{
case DS_NOT_YET_CHECKED:
/* Spurious wakeup as described above */
break;
case DS_NO_DEADLOCK:
case DS_SOFT_DEADLOCK:
{
StringInfoData buf;
const char *modename;
long secs;
int usecs;
long msecs;
initStringInfo(&buf);
DescribeLockTag(&buf, &locallock->tag.lock);
modename = GetLockmodeName(locallock->tag.lock.locktag_lockmethodid,
lockmode);
TimestampDifference(timeout_start_time,
GetCurrentTimestamp(),
&secs, &usecs);
msecs = secs * 1000 + usecs / 1000;
usecs = usecs % 1000;
if (deadlock_state == DS_SOFT_DEADLOCK)
ereport(LOG,
(errmsg("deadlock for %s on %s avoided by rearranging queue order after %ld.%03d ms",
modename, buf.data,
msecs, usecs)));
else if (MyProc->waitStatus == STATUS_WAITING)
ereport(LOG,
(errmsg("process %d still waiting for %s on %s after %ld.%03d ms",
MyProcPid, modename, buf.data,
msecs, usecs)));
else
ereport(LOG,
(errmsg("process %d acquired %s on %s after %ld.%03d ms",
MyProcPid, modename, buf.data,
msecs, usecs)));
pfree(buf.data);
break;
}
case DS_HARD_DEADLOCK:
/* ERROR will be reported below, so no message here */
break;
}
}
} while (MyProc->waitStatus == STATUS_WAITING);
/*
......@@ -1011,14 +1073,17 @@ ProcLockWakeup(LockMethod lockMethodTable, LOCK *lock)
* We only get to this routine if we got SIGALRM after DeadlockTimeout
* while waiting for a lock to be released by some other process. Look
* to see if there's a deadlock; if not, just return and continue waiting.
* (But signal ProcSleep to log a message, if log_lock_waits is true.)
* If we have a real deadlock, remove ourselves from the lock's wait queue
* and signal an error to ProcSleep.
*
* NB: this is run inside a signal handler, so be very wary about what is done
* here or in called routines.
*/
static void
CheckDeadLock(void)
{
int i;
DeadlockState deadlock_state = DS_DEADLOCK_NOT_FOUND;
/*
* Acquire exclusive lock on the entire shared lock data structures. Must
......@@ -1044,22 +1109,31 @@ CheckDeadLock(void)
* This is quicker than checking our semaphore's state, since no kernel
* call is needed, and it is safe because we hold the lock partition lock.
*/
if (MyProc->links.prev != INVALID_OFFSET &&
MyProc->links.next != INVALID_OFFSET)
deadlock_state = DeadLockCheck(MyProc);
if (MyProc->links.prev == INVALID_OFFSET ||
MyProc->links.next == INVALID_OFFSET)
goto check_done;
#ifdef LOCK_DEBUG
if (Debug_deadlocks)
DumpAllLocks();
#endif
/* Run the deadlock check, and set deadlock_state for use by ProcSleep */
deadlock_state = DeadLockCheck(MyProc);
if (deadlock_state == DS_HARD_DEADLOCK)
{
/*
* Oops. We have a deadlock.
*
* Get this process out of wait state. (Note: we could do this more
* efficiently by relying on lockAwaited, but use this coding to preserve
* the flexibility to kill some other transaction than the one detecting
* the deadlock.)
* Get this process out of wait state. (Note: we could do this more
* efficiently by relying on lockAwaited, but use this coding to
* preserve the flexibility to kill some other transaction than the
* one detecting the deadlock.)
*
* RemoveFromWaitQueue sets MyProc->waitStatus to STATUS_ERROR, so
* ProcSleep will report an error after we return from the signal handler.
* ProcSleep will report an error after we return from the signal
* handler.
*/
Assert(MyProc->waitLock != NULL);
RemoveFromWaitQueue(MyProc, LockTagHashCode(&(MyProc->waitLock->tag)));
......@@ -1071,50 +1145,35 @@ CheckDeadLock(void)
PGSemaphoreUnlock(&MyProc->sem);
/*
* We're done here. Transaction abort caused by the error that ProcSleep
* will raise will cause any other locks we hold to be released, thus
* allowing other processes to wake up; we don't need to do that here.
* NOTE: an exception is that releasing locks we hold doesn't consider the
* possibility of waiters that were blocked behind us on the lock we just
* failed to get, and might now be wakable because we're not in front of
* them anymore. However, RemoveFromWaitQueue took care of waking up any
* such processes.
* We're done here. Transaction abort caused by the error that
* ProcSleep will raise will cause any other locks we hold to be
* released, thus allowing other processes to wake up; we don't need
* to do that here. NOTE: an exception is that releasing locks we
* hold doesn't consider the possibility of waiters that were blocked
* behind us on the lock we just failed to get, and might now be
* wakable because we're not in front of them anymore. However,
* RemoveFromWaitQueue took care of waking up any such processes.
*/
}
else if (log_lock_waits)
{
/*
* Unlock my semaphore so that the interrupted ProcSleep() call can
* print the log message (we daren't do it here because we are inside
* a signal handler). It will then sleep again until someone
* releases the lock.
*/
PGSemaphoreUnlock(&MyProc->sem);
}
/*
* Release locks acquired at head of routine. Order is not critical, so
* do it back-to-front to avoid waking another CheckDeadLock instance
* before it can get all the locks.
*/
check_done:
for (i = NUM_LOCK_PARTITIONS; --i >= 0;)
LWLockRelease(FirstLockMgrLock + i);
/*
* Issue any log messages requested.
*
* Deadlock ERROR messages are issued as part of transaction abort, so
* these messages should not raise error states intentionally.
*/
if (log_lock_waits)
{
switch (deadlock_state)
{
case DS_SOFT_DEADLOCK:
ereport(LOG,
(errmsg("deadlock avoided by rearranging lock order")));
break;
case DS_DEADLOCK_NOT_FOUND:
ereport(LOG,
(errmsg("statement waiting for lock for at least %d ms",
DeadlockTimeout)));
break;
case DS_HARD_DEADLOCK:
break; /* ERROR message handled during abort */
default:
break;
}
}
}
......@@ -1211,8 +1270,8 @@ enable_sig_alarm(int delayms, bool is_statement_timeout)
* to the state variables. The deadlock checker may get run earlier
* than normal, but that does no harm.
*/
fin_time = GetCurrentTimestamp();
fin_time = TimestampTzPlusMilliseconds(fin_time, delayms);
timeout_start_time = GetCurrentTimestamp();
fin_time = TimestampTzPlusMilliseconds(timeout_start_time, delayms);
deadlock_timeout_active = true;
if (fin_time >= statement_fin_time)
return true;
......@@ -1221,6 +1280,9 @@ enable_sig_alarm(int delayms, bool is_statement_timeout)
{
/* Begin deadlock timeout with no statement-level timeout */
deadlock_timeout_active = true;
/* GetCurrentTimestamp can be expensive, so only do it if we must */
if (log_lock_waits)
timeout_start_time = GetCurrentTimestamp();
}
/* If we reach here, okay to set the timer interrupt */
......
src/backend/utils/misc/guc.c
View file @ 6e072287
......@@ -10,7 +10,7 @@
* Written by Peter Eisentraut <peter_e@gmx.net>.
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.398 2007/06/18 10:02:57 mha Exp $
* $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.399 2007/06/19 20:13:22 tgl Exp $
*
*--------------------------------------------------------------------
*/
......@@ -825,13 +825,14 @@ static struct config_bool ConfigureNamesBool[] =
#endif
{
{"log_lock_waits", PGC_SIGHUP, LOGGING_WHAT,
gettext_noop("Logs long lock wait events."),
{"log_lock_waits", PGC_SUSET, LOGGING_WHAT,
gettext_noop("Logs long lock waits."),
NULL
},
&log_lock_waits,
false, NULL, NULL
},
{
{"log_hostname", PGC_SIGHUP, LOGGING_WHAT,
gettext_noop("Logs the host name in the connection logs."),
......
src/include/storage/lmgr.h
View file @ 6e072287
......@@ -7,13 +7,14 @@
* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/storage/lmgr.h,v 1.57 2007/01/05 22:19:58 momjian Exp $
* $PostgreSQL: pgsql/src/include/storage/lmgr.h,v 1.58 2007/06/19 20:13:22 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#ifndef LMGR_H
#define LMGR_H
#include "lib/stringinfo.h"
#include "storage/lock.h"
#include "utils/rel.h"
......@@ -69,4 +70,7 @@ extern void UnlockSharedObject(Oid classid, Oid objid, uint16 objsubid,
/* Knowledge about which locktags describe temp objects */
extern bool LockTagIsTemp(const LOCKTAG *tag);
/* Describe a locktag for error messages */
extern void DescribeLockTag(StringInfo buf, const LOCKTAG *tag);
#endif /* LMGR_H */
src/include/storage/lock.h
View file @ 6e072287
......@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/storage/lock.h,v 1.105 2007/05/30 16:16:32 tgl Exp $
* $PostgreSQL: pgsql/src/include/storage/lock.h,v 1.106 2007/06/19 20:13:22 tgl Exp $
*
*-------------------------------------------------------------------------
*/
......@@ -397,10 +397,12 @@ typedef enum
/* Deadlock states identified by DeadLockCheck() */
typedef enum
{
DS_DEADLOCK_NOT_FOUND, /* no deadlock found within database server */
DS_SOFT_DEADLOCK, /* deadlock, but lock queues rearrangeable */
DS_NOT_YET_CHECKED, /* no deadlock check has run yet */
DS_NO_DEADLOCK, /* no deadlock detected */
DS_SOFT_DEADLOCK, /* deadlock avoided by queue rearrangement */
DS_HARD_DEADLOCK /* deadlock, no way out but ERROR */
} DeadlockState;
} DeadLockState;
/*
* The lockmgr's shared hash tables are partitioned to reduce contention.
......@@ -449,7 +451,7 @@ extern void lock_twophase_postcommit(TransactionId xid, uint16 info,
extern void lock_twophase_postabort(TransactionId xid, uint16 info,
void *recdata, uint32 len);
extern DeadlockState DeadLockCheck(PGPROC *proc);
extern DeadLockState DeadLockCheck(PGPROC *proc);
extern void DeadLockReport(void);
extern void RememberSimpleDeadLock(PGPROC *proc1,
LOCKMODE lockmode,
......
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