diff options
Diffstat (limited to 'libraries/ghc-boot/GHC/PackageDb.hs')
| -rw-r--r-- | libraries/ghc-boot/GHC/PackageDb.hs | 22 |
1 files changed, 14 insertions, 8 deletions
diff --git a/libraries/ghc-boot/GHC/PackageDb.hs b/libraries/ghc-boot/GHC/PackageDb.hs index bf83d25baa..9ce07e7484 100644 --- a/libraries/ghc-boot/GHC/PackageDb.hs +++ b/libraries/ghc-boot/GHC/PackageDb.hs @@ -239,15 +239,21 @@ lockPackageDbWith mode file = do -- DB for reading then we will require that the installer/packaging has -- included the lock file. -- - -- Thus the logic here is to first try opening in read-only mode (to handle - -- global read-only DBs) and if the file does not exist then try opening in - -- read/write mode to create the lock file. If either succeed then lock the - -- file. IO exceptions (other than the first open attempt failing due to the - -- file not existing) simply propagate. + -- Thus the logic here is to first try opening in read-write mode + -- and if that fails we try read-only (to handle global read-only DBs). + -- If either succeed then lock the file. IO exceptions (other than the first + -- open attempt failing due to the file not existing) simply propagate. + -- + -- Note that there is a complexity here which was discovered in #13945: some + -- filesystems (e.g. NFS) will only allow exclusive locking if the fd was + -- opened for write access. We would previously try opening the lockfile for + -- read-only access first, however this failed when run on such filesystems. + -- Consequently, we now try read-write access first, falling back to read-only + -- if are denied permission (e.g. in the case of a global database). catchJust - (\e -> if isDoesNotExistError e then Just () else Nothing) - (lockFileOpenIn ReadMode) - (const $ lockFileOpenIn ReadWriteMode) + (\e -> if isPermissionError e then Just () else Nothing) + (lockFileOpenIn ReadWriteMode) + (const $ lockFileOpenIn ReadMode) where lock = file <.> "lock" |