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inspector: more conservative minimum stack size #27855

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inspector: more conservative minimum stack size #27855

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inspector: more conservative minimum stack size
bnoordhuis May 24, 2019
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bnoordhuis Jun 1, 2019
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inspector: more conservative minimum stack size 
PTHREAD_STACK_MIN is 2 KB with musl, which is too small to safely
receive signals. PTHREAD_STACK_MIN + MINSIGSTKSZ is 8 KB on arm64,
which is the musl architecture with the biggest MINSIGSTKSZ so let's
use that as a lower bound and let's quadruple it just in case.
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bnoordhuis committed Jun 1, 2019
commit a28deaad9bf218fb1470af023807a2fb755e7275
16 changes: 11 additions & 5 deletions src/inspector_agent.cc
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Expand Up @@ -25,6 +25,7 @@
#include <climits> // PTHREAD_STACK_MIN
#endif // __POSIX__

#include <algorithm>
#include <cstring>
#include <sstream>
#include <unordered_map>
Expand Down Expand Up @@ -111,12 +112,17 @@ static int StartDebugSignalHandler() {
CHECK_EQ(0, uv_sem_init(&start_io_thread_semaphore, 0));
pthread_attr_t attr;
CHECK_EQ(0, pthread_attr_init(&attr));
// Don't shrink the thread's stack on FreeBSD. Said platform decided to
// follow the pthreads specification to the letter rather than in spirit:
// https://lists.freebsd.org/pipermail/freebsd-current/2014-March/048885.html
#ifndef __FreeBSD__
CHECK_EQ(0, pthread_attr_setstacksize(&attr, PTHREAD_STACK_MIN));
#endif // __FreeBSD__
// PTHREAD_STACK_MIN is 2 KB with musl libc, which is too small to safely
// receive signals. PTHREAD_STACK_MIN + MINSIGSTKSZ is 8 KB on arm64, which
// is the musl architecture with the biggest MINSIGSTKSZ so let's use that
// as a lower bound and let's quadruple it just in case. The goal is to avoid
// creating a big 2 or 4 MB address space gap (problematic on 32 bits
// because of fragmentation), not squeeze out every last byte.
const size_t stack_size = std::max(static_cast<size_t>(4 * 8192),
static_cast<size_t>(PTHREAD_STACK_MIN));
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@addaleax addaleax May 26, 2019

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I guess this doesn’t change anything compared to the current situation, but should we do something like libuv/libuv@38bb0f5 (use PTHREAD_STACK_MIN only inside an #ifdef)?

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@bnoordhuis bnoordhuis Jun 1, 2019

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Fair point. Addressed in the fix-up commit.

CHECK_EQ(0, pthread_attr_setstacksize(&attr, stack_size));
#endif // !__FreeBSD__
CHECK_EQ(0, pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED));
sigset_t sigmask;
// Mask all signals.
Expand Down