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* Concurrent GC on Cygwin.

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This commit is contained in:
Eelco Dolstra 2006-06-20 17:48:10 +00:00
parent cc51f9c539
commit dbf6d7e783
3 changed files with 146 additions and 73 deletions
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80
src/libstore/gc.cc
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@ -11,6 +11,11 @@
#include <fcntl.h>
#include <unistd.h>
#ifdef __CYGWIN__
#include <windows.h>
#include <sys/cygwin.h>
#endif
static string gcLockName = "gc.lock";
static string tempRootsDir = "temproots";
@ -108,10 +113,6 @@ static AutoCloseFD fdTempRoots;
void addTempRoot(const Path & path)
{
#ifdef __CYGWIN__
return;
#endif
/* Create the temporary roots file for this process. */
if (fdTempRoots == -1) {
@ -124,12 +125,24 @@ void addTempRoot(const Path & path)
AutoCloseFD fdGCLock = openGCLock(ltRead);
fdTempRoots = open(fnTempRoots.c_str(), O_RDWR | O_CREAT | O_TRUNC, 0600);
if (fdTempRoots == -1)
throw SysError(format("opening temporary roots file `%1%'") % fnTempRoots);
if (pathExists(fnTempRoots))
/* It *must* be stale, since there can be no two
processes with the same pid. */
deletePath(fnTempRoots);
fdTempRoots = openLockFile(fnTempRoots, true);
fdGCLock.close();
/* Note that on Cygwin a lot of the following complexity
is unnecessary, since we cannot delete open lock
files. If we have the lock file open, then it's valid;
if we can delete it, then it wasn't in use any more.
Also note that on Cygwin we cannot "upgrade" a lock
from a read lock to a write lock. */
#ifndef __CYGWIN__
debug(format("acquiring read lock on `%1%'") % fnTempRoots);
lockFile(fdTempRoots, ltRead, true);
@ -143,6 +156,10 @@ void addTempRoot(const Path & path)
/* The garbage collector deleted this file before we could
get a lock. (It won't delete the file after we get a
lock.) Try again. */
#else
break;
#endif
}
}
@ -155,9 +172,14 @@ void addTempRoot(const Path & path)
string s = path + '\0';
writeFull(fdTempRoots, (const unsigned char *) s.c_str(), s.size());
#ifndef __CYGWIN__
/* Downgrade to a read lock. */
debug(format("downgrading to read lock on `%1%'") % fnTempRoots);
lockFile(fdTempRoots, ltRead, true);
#else
debug(format("releasing write lock on `%1%'") % fnTempRoots);
lockFile(fdTempRoots, ltNone, true);
#endif
}
@ -176,10 +198,6 @@ typedef list<FDPtr> FDs;
static void readTempRoots(PathSet & tempRoots, FDs & fds)
{
#ifdef __CYGWIN__
return;
#endif
/* Read the `temproots' directory for per-process temporary root
files. */
Strings tempRootFiles = readDirectory(
@ -191,7 +209,19 @@ static void readTempRoots(PathSet & tempRoots, FDs & fds)
Path path = (format("%1%/%2%/%3%") % nixStateDir % tempRootsDir % *i).str();
debug(format("reading temporary root file `%1%'") % path);
#ifdef __CYGWIN__
/* On Cygwin we just try to delete the lock file. */
char win32Path[MAX_PATH];
cygwin_conv_to_full_win32_path(path.c_str(), win32Path);
if (DeleteFile(win32Path)) {
printMsg(lvlError, format("removed stale temporary roots file `%1%'")
% path);
continue;
} else
debug(format("delete of `%1%' failed: %2%") % path % GetLastError());
#endif
FDPtr fd(new AutoCloseFD(open(path.c_str(), O_RDWR, 0666)));
if (*fd == -1) {
/* It's okay if the file has disappeared. */
@ -199,6 +229,11 @@ static void readTempRoots(PathSet & tempRoots, FDs & fds)
throw SysError(format("opening temporary roots file `%1%'") % path);
}
/* This should work, but doesn't, for some reason. */
//FDPtr fd(new AutoCloseFD(openLockFile(path, false)));
//if (*fd == -1) continue;
#ifndef __CYGWIN__
/* Try to acquire a write lock without blocking. This can
only succeed if the owning process has died. In that case
we don't care about its temporary roots. */
@ -209,6 +244,7 @@ static void readTempRoots(PathSet & tempRoots, FDs & fds)
writeFull(*fd, (const unsigned char *) "d", 1);
continue;
}
#endif
/* Acquire a read lock. This will prevent the owning process
from upgrading to a write lock, therefore it will block in
@ -448,28 +484,24 @@ void collectGarbage(GCAction action, const PathSet & pathsToDelete,
debug(format("dead path `%1%'") % *i);
result.insert(*i);
AutoCloseFD fdLock;
if (action == gcDeleteDead || action == gcDeleteSpecific) {
#ifndef __CYGWIN__
AutoCloseFD fdLock;
/* Only delete a lock file if we can acquire a write lock
on it. That means that it's either stale, or the
process that created it hasn't locked it yet. In the
latter case the other process will detect that we
deleted the lock, and retry (see pathlocks.cc). */
if (i->size() >= 5 && string(*i, i->size() - 5) == ".lock") {
fdLock = open(i->c_str(), O_RDWR);
if (fdLock == -1) {
if (errno == ENOENT) continue;
throw SysError(format("opening lock file `%1%'") % *i);
}
if (!lockFile(fdLock, ltWrite, false)) {
fdLock = openLockFile(*i, false);
if (fdLock != -1 && !lockFile(fdLock, ltWrite, false)) {
debug(format("skipping active lock `%1%'") % *i);
continue;
}
}
#endif
printMsg(lvlInfo, format("deleting `%1%'") % *i);
@ -478,9 +510,11 @@ void collectGarbage(GCAction action, const PathSet & pathsToDelete,
deleteFromStore(*i, freed);
bytesFreed += freed;
#ifndef __CYGWIN__
if (fdLock != -1)
/* Write token to stale (deleted) lock file. */
writeFull(fdLock, (const unsigned char *) "d", 1);
#endif
}
}
}