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Fix #1429, adjust pthread stack to account for TCB+TLS #1430

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Dec 12, 2023
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Fix #1429, adjust pthread stack to account for TCB+TLS #1430

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37 changes: 21 additions & 16 deletions src/os/posix/src/os-impl-tasks.c
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Original file line number Diff line number Diff line change
Expand Up @@ -37,10 +37,26 @@
#include "os-shared-idmap.h"

/*
* Defines
* Extra Stack Space for overhead -
*
* glibc pthreads implicitly puts its TCB/TLS structures at the base of the stack.
* The actual size of these structures is highly system and configuration dependent.
* Experimentation/measurement on an x64-64 system with glibc shows this to consume
* between 9-10kB of stack space off the top.
*
* There does not seem to be a reliable/standardized way of determining how large this
* is going to be, but PTHREAD_STACK_MIN (if defined) should include adequate space for it.
* If this is not defined, then just assume 1 page.
*
* Importantly - when the user passes a stack size to OS_TaskCreate() - the expectation is
* that there will be at least this amount of real _usable_ space for the task. If 10kB
* is used before the entry point is even called, this needs to be accounted for, or else
* the stack might end up being too small.
*/
#ifndef PTHREAD_STACK_MIN
#define PTHREAD_STACK_MIN (8 * 1024)
#ifdef PTHREAD_STACK_MIN

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Code scanning / CodeQL

Conditional compilation Note

Use of conditional compilation must be kept to a minimum.
#define OS_IMPL_STACK_EXTRA PTHREAD_STACK_MIN
#else
#define OS_IMPL_STACK_EXTRA POSIX_GlobalVars.PageSize
#endif

/* Tables where the OS object information is stored */
Expand Down Expand Up @@ -451,20 +467,9 @@
}

/*
* Adjust the stack size parameter.
*
* POSIX has additional restrictions/limitations on the stack size of tasks that
* other RTOS environments may not have. Specifically POSIX says that the stack
* size must be at least PTHREAD_STACK_MIN and may also need to be a multiple of the
* system page size.
*
* Rounding up means the user might get a bigger stack than they requested, but
* that should not break anything aside from consuming extra memory.
* Adjust the stack size parameter, add budget for TCB/TLS overhead.
*/
if (stacksz < PTHREAD_STACK_MIN)
{
stacksz = PTHREAD_STACK_MIN;
}
stacksz += OS_IMPL_STACK_EXTRA;

stacksz += POSIX_GlobalVars.PageSize - 1;
stacksz -= stacksz % POSIX_GlobalVars.PageSize;
Expand Down