src: fix race condition in debug signal on exit #3528
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bnoordhuis
added
c++
| static void TryStartDebugger() { | ||
| // Call only async signal-safe functions here! Don't retry the exchange, | ||
| // it will deadlock when the thread is interrupted inside a critical section. | ||
| if (auto isolate = node_isolate.exchange(nullptr)) { |
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Hmmm, our linter doesn't complain about this?
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Why would it? It's a common C++ idiom.
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LGTM |
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LGTM |
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OS X... |
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@bnoordhuis .. ugh. |
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Hacked together a crummy workaround. I'll refine it further but first let's see if the basic approach works: https://ci.nodejs.org/job/node-test-pull-request/619/ |
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Alternate take: https://ci.nodejs.org/job/node-test-pull-request/621/ |
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Having to polyfill atomic makes me sad. Otherwise LGTM. |
| template <typename T> | ||
| struct atomic { | ||
| atomic() = default; | ||
| T exchange(T value) { return __sync_lock_test_and_set(&value_, value); } |
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LGTM, if it works |
Before this commit, sending a SIGUSR1 at program exit could trigger a hard to reproduce race condition where `v8::Debug::DebugBreak(isolate)` got called when the isolate was in the process of being torn down. A similar race condition is in theory possible when sending signals to two threads simultaneously but I haven't been able to reproduce that myself (and I tried, oh how I tried.) This commit fixes the race condition by turning `node_isolate` into a `std::atomic` and using it as an ad hoc synchronization primitive in places where that is necessary. A bare minimum std::atomic polyfill is added for OS X because Apple wouldn't be Apple if things just worked out of the box. PR-URL: nodejs#3528 Reviewed-By: Fedor Indutny <[email protected]> Reviewed-By: James M Snell <[email protected]>
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lol |
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@bnoordhuis ... is this something that should go into LTS or not? |
bnoordhuis
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Oct 28, 2015
Before this commit, sending a SIGUSR1 at program exit could trigger a hard to reproduce race condition where `v8::Debug::DebugBreak(isolate)` got called when the isolate was in the process of being torn down. A similar race condition is in theory possible when sending signals to two threads simultaneously but I haven't been able to reproduce that myself (and I tried, oh how I tried.) This commit fixes the race condition by turning `node_isolate` into a `std::atomic` and using it as an ad hoc synchronization primitive in places where that is necessary. A bare minimum std::atomic polyfill is added for OS X because Apple wouldn't be Apple if things just worked out of the box. PR-URL: #3528 Reviewed-By: Fedor Indutny <[email protected]> Reviewed-By: James M Snell <[email protected]>
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Landed in v4.x-staging in c85736e |
rvagg
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Oct 29, 2015
Before this commit, sending a SIGUSR1 at program exit could trigger a hard to reproduce race condition where `v8::Debug::DebugBreak(isolate)` got called when the isolate was in the process of being torn down. A similar race condition is in theory possible when sending signals to two threads simultaneously but I haven't been able to reproduce that myself (and I tried, oh how I tried.) This commit fixes the race condition by turning `node_isolate` into a `std::atomic` and using it as an ad hoc synchronization primitive in places where that is necessary. A bare minimum std::atomic polyfill is added for OS X because Apple wouldn't be Apple if things just worked out of the box. PR-URL: nodejs#3528 Reviewed-By: Fedor Indutny <[email protected]> Reviewed-By: James M Snell <[email protected]>
bnoordhuis
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Oct 29, 2015
Before this commit, sending a SIGUSR1 at program exit could trigger a hard to reproduce race condition where `v8::Debug::DebugBreak(isolate)` got called when the isolate was in the process of being torn down. A similar race condition is in theory possible when sending signals to two threads simultaneously but I haven't been able to reproduce that myself (and I tried, oh how I tried.) This commit fixes the race condition by turning `node_isolate` into a `std::atomic` and using it as an ad hoc synchronization primitive in places where that is necessary. A bare minimum std::atomic polyfill is added for OS X because Apple wouldn't be Apple if things just worked out of the box. PR-URL: #3528 Reviewed-By: Fedor Indutny <[email protected]> Reviewed-By: James M Snell <[email protected]>
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Before this commit, sending a SIGUSR1 at program exit could trigger a
hard to reproduce race condition where
v8::Debug::DebugBreak(isolate)got called when the isolate was in the process of being torn down.
A similar race condition is in theory possible when sending signals
to two threads simultaneously but I haven't been able to reproduce
that myself (and I tried, oh how I tried.)
This commit fixes the race condition by turning
node_isolateintoa
std::atomicand using it as an ad hoc synchronization primitivein places where that is necessary.
R=@indutny?
CI: https://ci.nodejs.org/job/node-test-pull-request/615/