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Mac allow system ucontext #90

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merged 2 commits into from
Sep 8, 2021
Merged

Mac allow system ucontext #90

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c9ddfe3
allow use of system ucontext on macs and warn m1 users to do just tha…
olivier-snl Aug 3, 2021
ee4a774
also mention required define for mac to use system ucontext
olivier-snl Aug 4, 2021
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6 changes: 3 additions & 3 deletions config/qthread_check_swapcontext.m4
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Original file line number Diff line number Diff line change
Expand Up @@ -65,9 +65,9 @@ AC_CACHE_CHECK([whether swapcontext works properly],
[qthread_cv_swapcontext_works],
[
case "$host" in
*-darwin*)
qthread_cv_swapcontext_works=no
;;
# *-darwin*)
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Since current x86 and M1 Macs seemingly support system ucontext, I think it is ok to drop this case statement.

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@janciesko janciesko Sep 7, 2021 •
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Consider adding something like
AS_IF([test "$host" in *-darvin*], [qt_host_based_enable_fastcontext=no], [qt_host_based_enable_fastcontext=yes] ;;
to L37 to disable fast context automatically on M1 Macs while the support is not available yet.

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darvin -> darwin. But really, it's the combo of darwin and aarch64 (however that parses). We don't want to disable fast context on earlier macs.

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@janciesko janciesko Sep 7, 2021 •
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Yes, that combo should come together in L37 if I see this correctly when adding that additional check for Darwin.

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https://github.com/janciesko/qthreads/tree/mac-allow-system-ucontext-2

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https://github.com/janciesko/qthreads/tree/mac-allow-system-ucontext-2

This is not correct. m1 macs are arm v8 not arm v7. The arch to AC will be something like arm64 or aarch64.

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Yes, this was more an idea / place holder. We'd need to add the right case depending on what config gives us.

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We can match on aarch64-*-darwin* | arm64*-*-darwin*

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Actually, since it shouldn't really match any of the architectures in the case, it should fall through without any change. I just tried from the qthreads repo branch (without the m4 change and without the disable fast context switch on configure) and it worked just fine.

# qthread_cv_swapcontext_works=no
# ;;
*)
AC_RUN_IFELSE([AC_LANG_SOURCE([[
#include <ucontext.h>
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2 changes: 1 addition & 1 deletion src/fastcontext/asm.S
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Expand Up @@ -43,7 +43,7 @@
# define SET _qt_setmctxt
# define GET _qt_getmctxt
# else
# error What kind of a Mac is this?
# error What kind of a Mac is this? If M1, use CFLAGS=-D_XOPEN_SOURCE and --disable-fastcontext --with-default-stack-size=65536 in configure.
# endif
#elif defined(__linux__)
# if (QTHREAD_ASSEMBLY_ARCH == QTHREAD_ARM)
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