Commit graph

19 commits

Author SHA1 Message Date
Eelco Dolstra
e349f2c0a3
Use BSD instead of POSIX file locks
POSIX file locks are essentially incompatible with multithreading. BSD
locks have much saner semantics. We need this now that there can be
multiple concurrent LocalStore::buildPaths() invocations.
2019-08-02 18:39:16 +02:00
Eelco Dolstra
4f09ce7940
Fix 'deadlock: trying to re-acquire self-held lock'
This was caused by derivations with 'allowSubstitutes = false'. Such
derivations will be built locally. However, if there is another
SubstitionGoal that has the output of the first derivation in its
closure, then the path will be simultaneously built and substituted.

There was a check to catch this situation (via pathIsLockedByMe()),
but it no longer worked reliably because substitutions are now done in
another thread. (Thus the comment 'It can't happen between here and
the lockPaths() call below because we're not allowing multi-threading'
was no longer valid.)

The fix is to handle the path already being locked in both
SubstitutionGoal and DerivationGoal.
2018-02-12 17:06:06 +01:00
Eelco Dolstra
a55f589720
openLockFile: Return an AutoCloseFD 2017-01-26 20:40:33 +01:00
Eelco Dolstra
5e51ffb1c2 Support sandbox builds by non-root users
This allows an unprivileged user to perform builds on a diverted store
(i.e. where the physical store location differs from the logical
location).

Example:

  $ NIX_LOG_DIR=/tmp/log NIX_REMOTE="local?real=/tmp/store&state=/tmp/var" nix-build -E \
    'with import <nixpkgs> {}; runCommand "foo" { buildInputs = [procps nettools]; } "id; ps; ifconfig; echo $out > $out"'

will do a build in the Nix store physically in /tmp/store but
logically in /nix/store (and thus using substituters for the latter).
2016-06-03 15:59:28 +02:00
Eelco Dolstra
b7fd2c2822 Use "#pragma once" to prevent repeated header file inclusion 2012-07-18 14:59:03 -04:00
Eelco Dolstra
4e17be7981 * Revert r19797, and use a simpler solution: just don't monitor build
hooks for silence.  It's unnecessary because the remote nix-store
  command is already monitoring the real build.
2010-02-03 21:38:41 +00:00
Eelco Dolstra
f859a8d3c3 * While waiting for a lock, print a sign of life every 5 minutes.
This prevents remote builders from being killed by the
  `max-silent-time' inactivity monitor while they are waiting for a
  long garbage collection to finish.  This happens fairly often in the
  Hydra build farm.
2010-02-03 21:22:57 +00:00
Eelco Dolstra
4bbbe25802 * Remove most Cygwin-specific code. Cygwin 1.7 implements advisory
POSIX locks, and simulates Unix-style file deletion semantics
  sufficiently.  Note that this means that Nix won't work on Cygwin
  1.5 anymore.
2010-02-02 15:28:36 +00:00
Eelco Dolstra
cacff1be88 * No longer block while waiting for a lock on a store path. Instead
poll for it (i.e. if we can't acquire the lock, then let the main
  select() loop wait for at most a few seconds and then try again).
  This improves parallelism: if two nix-store processes are both
  trying to build a path at the same time, the second one shouldn't
  block; it should first see if it can build other goals.  Also, it
  prevents the deadlocks that have been occuring in Hydra lately,
  where a process waits for a lock held by another process that's
  waiting for a lock held by the first.

  The downside is that polling isn't really elegant, but POSIX doesn't
  provide a way to wait for locks in a select() loop.  The only
  solution would be to spawn a thread for each lock to do a blocking
  fcntl() and then signal the main thread, but that would require
  pthreads.
2009-03-23 01:05:54 +00:00
Eelco Dolstra
824b154ce8 * Release output locks as soon as possible, not when the destructor of
the DerivationGoal runs.  Otherwise, if a goal is a top-level goal,
  then the lock won't be released until nix-store finishes.  With
  --keep-going and lots of top-level goals, it's possible to run out
  of file descriptors (this happened sometimes in the build farm for
  Nixpkgs).  Also, for failed derivation, it won't be possible to
  build it again  until the lock is released.
  
* Idem for locks on build users: these weren't released in a timely
  manner for failed top-level derivation goals.  So if there were more
  than (say) 10 such failed builds, you would get an error about
  having run out of build users.
2009-02-16 09:24:20 +00:00
Eelco Dolstra
bd955e15e1 * GCC 4.3.0 (Fedora 9) compatibility fixes. Reported by Gour and
Armijn Hemel.
2008-05-21 11:17:31 +00:00
Eelco Dolstra
c970b28ba0 * Fix a race condition with parallel builds where multiple
fixed-output derivations or substitutions try to build the same
  store path at the same time.  Locking generally catches this, but
  not between multiple goals in the same process.  This happened
  especially often (actually, only) in the build farm with fetchurl
  downloads of the same file being executed on multiple machines and
  then copied back to the main machine where they would clobber each
  other (NIXBF-13).

  Solution: if a goal notices that the output path is already locked,
  then go to sleep until another goal finishes (hopefully the one
  locking the path) and try again.
2007-08-28 11:36:17 +00:00
Eelco Dolstra
75068e7d75 * Use a proper namespace.
* Optimise header file usage a bit.
* Compile the parser as C++.
2006-09-04 21:06:23 +00:00
Eelco Dolstra
dbf6d7e783 * Concurrent GC on Cygwin. 2006-06-20 17:48:10 +00:00
Eelco Dolstra
588cb0eade * In `nix-env -i|-u|-e', lock the profile to prevent races between
concurrent nix-env operations on the same profile.  Fixes NIX-7.
2006-06-15 11:56:49 +00:00
Eelco Dolstra
59682e6188 * Make lock removal safe by signalling to blocked processes that the
lock they are waiting on has become stale (we do this by writing a
  meaningless token to the unlinked file).
2005-01-27 12:19:25 +00:00
Eelco Dolstra
c8d3882cdc * True parallel builds. Nix can now run as many build jobs in
parallel as possible (similar to GNU Make's `-j' switch).  This is
  useful on SMP systems, but it is especially useful for doing builds
  on multiple machines.  The idea is that a large derivation is
  initiated on one master machine, which then distributes
  sub-derivations to any number of slave machines.  This should not
  happen synchronously or in lock-step, so the master must be capable
  of dealing with multiple parallel build jobs.  We now have the
  infrastructure to support this.

  TODO: substitutes are currently broken.
2004-05-11 18:05:44 +00:00
Eelco Dolstra
7a02d95418 * Remove lock files after building. 2003-11-21 16:05:19 +00:00
Eelco Dolstra
9f0f020929 * libnix -> libstore. 2003-11-18 10:55:27 +00:00
Renamed from src/libnix/pathlocks.hh (Browse further)