V8: avoid deadlock when profiling is active

A deadlock happens when sampler initiated by SIGPROF tries to lock
the thread and the thread is already locked by the same thread. As
a result, other thread involved in sampling process hangs. The
patch adds a check for thread lock before continuing sampler
operation.

The fix has been tested on a sample app under load with and without
profiling turned on.

Fixes issue nodejs#14576 and specifically the duplicate issue nodejs#25295

V8: avoid deadlock when profiling is active

A deadlock happens when sampler initiated by SIGPROF tries to lock
the thread and the thread is already locked by the same thread. As
a result, other thread involved in sampling process hangs. The
patch adds a check for thread lock before continuing sampler
operation.

The fix has been tested on a sample app under load with and without
profiling turned on.

Fixes issue nodejs#14576 and specifically the duplicate issue nodejs#25295

Reviewed-By: Julien Gilli <julien.gilli@joyent.com>
PR-URL: nodejs#25309

2015.05.22, Version 0.12.4 (Stable)

* npm: upgrade to 2.10.1

* V8: revert v8 Array.prototype.values() removal (cjihrig)

* win: bring back xp/2k3 support (Bert Belder)

2015.05.13, Version 0.12.3 (Stable)

* V8: update to 3.28.71.19

* uv: upgrade to 1.5.0

* npm: upgrade to 2.9.1

* V8: don't busy loop in v8 cpu profiler thread (Mike Tunnicliffe)

* V8: fix issue with let bindings in for loops (adamk)

* debugger: don't spawn child process in remote mode (Jackson Tian)

* net: do not set V4MAPPED on FreeBSD (Julien Gilli)

* repl: make 'Unexpected token' errors recoverable (Julien Gilli)

* src: backport ignore ENOTCONN on shutdown race (Ben Noordhuis)

* src: fix backport of SIGINT crash fix on FreeBSD (Julien Gilli)

2015.03.31, Version 0.12.2 (Stable)

* uv: Upgrade to 1.4.2

* npm: Upgrade to 2.7.4

* V8: do not add extra newline in log file (Julien Gilli)

* V8: Fix --max_old_space_size=4096 integer overflow (Andrei Sedoi)

* asyncwrap: fix constructor condition for early ret (Trevor Norris)

* buffer: align chunks on 8-byte boundary (Fedor Indutny)

* buffer: fix pool offset adjustment (Trevor Norris)

* build: fix use of strict aliasing (Trevor Norris)

* console: allow Object.prototype fields as labels (Colin Ihrig)

* fs: make F_OK/R_OK/W_OK/X_OK not writable (Jackson Tian)

* fs: properly handle fd passed to truncate() (Bruno Jouhier)

* http: fix assert on data/end after socket error (Fedor Indutny)

* lib: fix max size check in Buffer constructor (Ben Noordhuis)

* lib: fix stdio/ipc sync i/o regression (Ben Noordhuis)

* module: replace NativeModule.require (Herbert Vojčík)

* net: allow port 0 in connect() (cjihrig)

* net: unref timer in parent sockets (Fedor Indutny)

* path: refactor for performance and consistency (Nathan Woltman)

* smalloc: extend user API (Trevor Norris)

* src: fix for SIGINT crash on FreeBSD (Fedor Indutny)

* src: fix builtin modules failing with --use-strict (Julien Gilli)

* watchdog: fix timeout for early polling return (Saúl Ibarra Corretgé)

2015.03.23, Version 0.12.1 (Stable)

* openssl: upgrade to 1.0.1m (Addressing multiple CVES)

2015.03.23, Version 0.10.38 (Maintenance)

* openssl: upgrade to 1.0.1m (Addressing multiple CVEs)

2015.03.11, Version 0.10.37 (Maintenance)

* uv: update to 0.10.36 (CVE-2015-0278)

* domains: fix stack clearing after error handled (Jonas Dohse)

* buffer: reword Buffer.concat error message (Chris Dickinson)

* console: allow Object.prototype fields as labels (Julien Gilli)

* V8: log version in profiler log file (Ben Noordhuis)

* http: fix performance regression for GET requests (Florin-Cristian Gavrila)

2015.02.06, Version 0.12.0 (Stable)

* npm: Upgrade to 2.5.1

* mdb_v8: update for v0.12 (Dave Pacheco)

2015.01.29, Version 0.11.16 (Unstable)

* openssl: Upgrade to 1.0.1l

* npm: Upgrade to 2.3.0

* url: revert support of `path` for url.format" (Julien Gilli)

* assert: use util.inspect() to create error messages (cjihrig)

* net: throw on invalid socket timeouts (cjihrig)

* url: fix parsing of ssh urls (Evan Lucas)