* normaliseFState() now locks all output paths prior to building, thus

ensuring that simultaneous invocations of Nix don't clobber
  each other's  builds.

* Fixed a bug in `make install'.
This commit is contained in:
Eelco Dolstra 2003-08-01 14:11:19 +00:00
parent 9df93f30bd
commit 545145cd58
5 changed files with 151 additions and 30 deletions

View file

@ -22,7 +22,7 @@ noinst_LIBRARIES = libnix.a libshared.a
libnix_a_SOURCES = util.cc hash.cc archive.cc md5.c \
store.cc fstate.cc normalise.cc exec.cc \
globals.cc db.cc references.cc
globals.cc db.cc references.cc pathlocks.cc
libshared_a_SOURCES = shared.cc
@ -44,6 +44,7 @@ install-data-local:
$(INSTALL) -d $(localstatedir)/nix
$(INSTALL) -d $(localstatedir)/nix/db
$(INSTALL) -d $(localstatedir)/nix/links
rm -f $(prefix)/current
ln -sf $(localstatedir)/nix/links/current $(prefix)/current
$(INSTALL) -d $(localstatedir)/log/nix
$(INSTALL) -d $(prefix)/store

View file

@ -4,6 +4,7 @@
#include "references.hh"
#include "db.hh"
#include "exec.hh"
#include "pathlocks.hh"
#include "globals.hh"
@ -23,7 +24,29 @@ static FSId storeSuccessor(const FSId & id1, ATerm sc)
}
typedef set<FSId> FSIdSet;
static FSId useSuccessor(const FSId & id)
{
string idSucc;
if (nixDB.queryString(noTxn, dbSuccessors, id, idSucc)) {
debug(format("successor %1% -> %2%") % (string) id % idSucc);
return parseHash(idSucc);
} else
return id;
}
typedef map<string, FSId> OutPaths;
typedef map<string, SliceElem> ElemMap;
Strings pathsFromOutPaths(const OutPaths & ps)
{
Strings ss;
for (OutPaths::const_iterator i = ps.begin();
i != ps.end(); i++)
ss.push_back(i->first);
return ss;
}
FSId normaliseFState(FSId id, FSIdSet pending)
@ -32,19 +55,66 @@ FSId normaliseFState(FSId id, FSIdSet pending)
/* Try to substitute $id$ by any known successors in order to
speed up the rewrite process. */
string idSucc;
while (nixDB.queryString(noTxn, dbSuccessors, id, idSucc)) {
debug(format("successor %1% -> %2%") % (string) id % idSucc);
id = parseHash(idSucc);
}
id = useSuccessor(id);
/* Get the fstate expression. */
FState fs = parseFState(termFromId(id));
/* It this is a normal form (i.e., a slice) we are done. */
/* If this is a normal form (i.e., a slice) we are done. */
if (fs.type == FState::fsSlice) return id;
if (fs.type != FState::fsDerive) abort();
/* Otherwise, it's a derivation. */
/* Otherwise, it's a derive expression, and we have to build it to
determine its normal form. */
/* Some variables. */
/* Output paths, with their ids. */
OutPaths outPaths;
/* Input paths, with their slice elements. */
ElemMap inMap;
/* Referencable paths (i.e., input and output paths). */
Strings refPaths;
/* The environment to be passed to the builder. */
Environment env;
/* Parse the outputs. */
for (DeriveOutputs::iterator i = fs.derive.outputs.begin();
i != fs.derive.outputs.end(); i++)
{
debug(format("building %1% in `%2%'") % (string) i->second % i->first);
outPaths[i->first] = i->second;
refPaths.push_back(i->first);
}
/* Obtain locks on all output paths. The locks are automatically
released when we exit this function or Nix crashes. */
PathLocks outputLock(pathsFromOutPaths(outPaths));
/* Now check again whether there is a successor. This is because
another process may have started building in parallel. After
it has finished and released the locks, we can (and should)
reuse its results. (Strictly speaking the first successor
check above can be omitted, but that would be less efficient.)
Note that since we now hold the locks on the output paths, no
other process can build this expression, so no further checks
are necessary. */
{
FSId id2 = useSuccessor(id);
if (id2 != id) {
FState fs = parseFState(termFromId(id2));
debug(format("skipping build of %1%, someone beat us to it")
% (string) id);
if (fs.type != FState::fsSlice) abort();
return id2;
}
}
/* Right platform? */
if (fs.derive.platform != thisSystem)
@ -52,14 +122,12 @@ FSId normaliseFState(FSId id, FSIdSet pending)
% fs.derive.platform % thisSystem);
/* Realise inputs (and remember all input paths). */
typedef map<string, SliceElem> ElemMap;
ElemMap inMap;
for (FSIds::iterator i = fs.derive.inputs.begin();
i != fs.derive.inputs.end(); i++) {
FSId nf = normaliseFState(*i, pending);
realiseSlice(nf, pending);
/* !!! nf should be a root of the garbage collector while we
are building */
FState fs = parseFState(termFromId(nf));
if (fs.type != FState::fsSlice) abort();
for (SliceElems::iterator j = fs.slice.elems.begin();
@ -67,27 +135,14 @@ FSId normaliseFState(FSId id, FSIdSet pending)
inMap[j->path] = *j;
}
Strings inPaths;
for (ElemMap::iterator i = inMap.begin(); i != inMap.end(); i++)
inPaths.push_back(i->second.path);
refPaths.push_back(i->second.path);
/* Build the environment. */
Environment env;
for (StringPairs::iterator i = fs.derive.env.begin();
i != fs.derive.env.end(); i++)
env[i->first] = i->second;
/* Parse the outputs. */
typedef map<string, FSId> OutPaths;
OutPaths outPaths;
for (DeriveOutputs::iterator i = fs.derive.outputs.begin();
i != fs.derive.outputs.end(); i++)
{
debug(format("building %1% in `%2%'") % (string) i->second % i->first);
outPaths[i->first] = i->second;
inPaths.push_back(i->first);
}
/* We can skip running the builder if we can expand all output
paths from their ids. */
bool fastBuild = true;
@ -132,7 +187,7 @@ FSId normaliseFState(FSId id, FSIdSet pending)
registerPath(path, i->second);
fs.slice.roots.push_back(i->second);
Strings refs = filterReferences(path, inPaths);
Strings refs = filterReferences(path, refPaths);
SliceElem elem;
elem.path = path;

48
src/pathlocks.cc Normal file
View file

@ -0,0 +1,48 @@
#include <fcntl.h>
#include "pathlocks.hh"
PathLocks::PathLocks(const Strings & _paths)
{
/* Note that `fds' is built incrementally so that the destructor
will only release those locks that we have already acquired. */
/* Sort the paths. This assures that locks are always acquired in
the same order, thus preventing deadlocks. */
Strings paths(_paths);
paths.sort();
/* Acquire the lock for each path. */
for (Strings::iterator i = paths.begin(); i != paths.end(); i++) {
string path = *i;
string lockPath = path + ".lock";
debug(format("locking path `%1%'") % path);
/* Open/create the lock file. */
int fd = open(lockPath.c_str(), O_WRONLY | O_CREAT, 0666);
if (fd == -1)
throw SysError(format("opening lock file `%1%'") % lockPath);
fds.push_back(fd);
/* Lock it. */
struct flock lock;
lock.l_type = F_WRLCK; /* exclusive lock */
lock.l_whence = SEEK_SET;
lock.l_start = 0;
lock.l_len = 0; /* entire file */
while (fcntl(fd, F_SETLKW, &lock) == -1)
if (errno != EINTR)
throw SysError(format("acquiring lock on `%1%'") % lockPath);
}
}
PathLocks::~PathLocks()
{
for (list<int>::iterator i = fds.begin(); i != fds.end(); i++)
close(*i);
}

18
src/pathlocks.hh Normal file
View file

@ -0,0 +1,18 @@
#ifndef __PATHLOCKS_H
#define __PATHLOCKS_H
#include "util.hh"
class PathLocks
{
private:
list<int> fds;
public:
PathLocks(const Strings & _paths);
~PathLocks();
};
#endif /* !__PATHLOCKS_H */

View file

@ -260,7 +260,6 @@ void addToStore(string srcPath, string & dstPath, FSId & id,
dstPath = canonPath(nixStore + "/" + (string) id + "-" + baseName);
try {
/* !!! should not use the substitutes! */
dstPath = expandId(id, deterministicName ? dstPath : "",
nixStore, FSIdSet(), true);
return;