diff options
Diffstat (limited to 'src')
-rw-r--r-- | src/libstore/gc.cc | 44 |
1 files changed, 29 insertions, 15 deletions
diff --git a/src/libstore/gc.cc b/src/libstore/gc.cc index c89f7a8a1ee4..cff503784520 100644 --- a/src/libstore/gc.cc +++ b/src/libstore/gc.cc @@ -12,17 +12,30 @@ #include <unistd.h> -/* Acquire the global GC lock. */ -static AutoCloseFD openGCLock(LockType lockType) +static string gcLockName = "gc.lock"; + + +/* Acquire the global GC lock. This is used to prevent new Nix + processes from starting after the temporary root files have been + read. To be precise: when they try to create a new temporary root + file, they will block until the garbage collector has finished / + yielded the GC lock. */ +static int openGCLock(LockType lockType) { -#if 0 - Path fnGCLock = (format("%1%/%2%/%3%") - % nixStateDir % tempRootsDir % getpid()).str(); + Path fnGCLock = (format("%1%/%2%") + % nixStateDir % gcLockName).str(); - fdTempRoots = open(fnTempRoots.c_str(), O_RDWR | O_CREAT | O_TRUNC, 0600); - if (fdTempRoots == -1) - throw SysError(format("opening temporary roots file `%1%'") % fnTempRoots); -#endif + AutoCloseFD fdGCLock = open(fnGCLock.c_str(), O_RDWR | O_CREAT, 0600); + if (fdGCLock == -1) + throw SysError(format("opening global GC lock `%1%'") % fnGCLock); + + lockFile(fdGCLock, lockType, true); + + /* !!! Restrict read permission on the GC root. Otherwise any + process that can open the file for reading can DoS the + collector. */ + + return fdGCLock.borrow(); } @@ -41,11 +54,15 @@ void addTempRoot(const Path & path) while (1) { fnTempRoots = (format("%1%/%2%/%3%") % nixStateDir % tempRootsDir % getpid()).str(); - + + 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); + fdGCLock.close(); + debug(format("acquiring read lock on `%1%'") % fnTempRoots); lockFile(fdTempRoots, ltRead, true); @@ -188,14 +205,11 @@ void collectGarbage(const PathSet & roots, GCAction action, { result.clear(); - /* !!! TODO: Acquire the global GC root. This prevents + /* Acquire the global GC root. This prevents a) New roots from being added. b) Processes from creating new temporary root files. */ + AutoCloseFD fdGCLock = openGCLock(ltWrite); - /* !!! Restrict read permission on the GC root. Otherwise any - process that can open the file for reading can DoS the - collector. */ - /* Determine the live paths which is just the closure of the roots under the `references' relation. */ PathSet livePaths; |