There seems to be no rationale reason for _cygtls::spinning to exist,
so it has been removed. _cygtls::spinning was introduced in the commit
edc4f86ad282A, and this flag means that another thread is waiting to
acquire _cygtls::stacklock. It is checked in the sig thread in _cygtls::
interrupt_now(), and if spinning is true, the interrupt will be delayed.
However, in this case, _cygtls::incyg is also set, so it is supposed to
be covered by _cygtls::incyg flag and does not seem to add any value.
If some problems happen in the signal handling, it might be a good idea
to revert this commit and check if the issue will be fixed.
Reviewed-by: Corinna Vinschen <corinna@vinschen.de>
Signed-off-by: Takashi Yano <takashi.yano@nifty.ne.jp>
Per the comment in _cygtls::interrupt_now(), the spinning flag
is supposed to guard that the targeted thread is about to enter
the Cygwin DLL. Setting spinning has then been added to _sigfe,
_sigbe, sigdelayed and stabilize_sig_stack, the latter being called
from setjmp/longjmp.
However, setjmp/longjmp only enter the DLL in case of a pending
signal, calling _cygtls::call_signal_handler(). This in turn is
already guarded by setting the incyg flag, and there's no other
action in stabilize_sig_stack which might interfere with the
signal setup. All the rest of setjmp/longjmp is plain userspace.
Therefore, drop setting the spinning flag from stabilize_sig_stack,
because it results in dropped signals in tight longjmp loops.
Fixes: edc4f86ad2 ("* Makefile.in (clean): Remove sigfe.s.")
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
Commit 0b6fbd396c ("* exceptions.cc (_cygtls::interrupt_now): Revert
to checking for "spinning" when choosing to defer signal.") introduced
a bug in the loop inside the stabilize_sig_stack subroutine:
First, stabilize_sig_stack grabs the stacklock. The _cygtls::incyg
flag is then incremented before checking if a signal has to be handled
for the current thread.
If no signal waits, the code simply jumps out, decrements _cygtls::incyg
and returns to the caller, which eventually releases the stacklock.
However, if a signal is waiting, stabilize_sig_stack releases the
stacklock, calls _cygtls::call_signal_handler(), and returns to
the start of the subroutine, trying to grab the lock.
After grabbing the lock, it increments _cygtls::incyg... wait...
again?
The loop does not decrement _cygtls::incyg after
_cygtls::call_signal_handler(), which returns with _cygtls::incyg
set to 1. So it increments incyg to 2. If no other signal is
waiting, stabilize_sig_stack jumps out and decrements _cygtls::incyg
to 1. Eventually, setjmp or longjmp both will return to user
code with _cygtls::incyg set to 1. This *may* be fixed at some later
point when signals arrive, but there will be a time when the application
runs in user code with broken signal handling.
Fixes: 0b6fbd396c ("* exceptions.cc (_cygtls::interrupt_now): Revert to checking for "spinning" when choosing to defer signal.")
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
This patch calls Sleep(0) in the wait loop in lock() to increase the
chance of being unlocked in other threads. The lock(), unlock() and
locked() are moved from sigfe.s to cygtls.h so that allows inline
expansion.
Addresses: https://cygwin.com/pipermail/cygwin/2024-November/256744.html
Fixes: 61522196c7 ("* Merge in cygwin-64bit-branch.")
Reported-by: Christian Franke <Christian.Franke@t-online.de>
Reviewed-by: Corinna Vinschen <corinna@vinschen.de>
Signed-off-by: Takashi Yano <takashi.yano@nifty.ne.jp>
The currently handled signal in a thread is called _cygtls::sig.
The variable name "sig" is used pretty often in the Cygwin source.
This makes it tricky to distinguish the currently handled signal
from any other usage of "sig".
Therefore, rename _cygtls::sig to _cygtls::current_sig
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
Previously, sigfe had a bug that the signal handler destroys fpu state.
This is caused by fninit instruction in sigdelayed. With this patch,
saving/restoring the FPU/SIMD state is done using fxsave/fxrstor or
xsave/xrstor rather than fnstcw/fldcw, stmxcsr/ldmxcsr and push/pop
xmm0-xmm15. Since xsave/xrstor is used, not only x87/MMX/SSE states
but also AVX/AVX2/AVX-512 states can be maintained unlike before.
Addresses: https://cygwin.com/pipermail/cygwin/2024-October/256503.html
Fixes: ed89fbc3ff ("* gendef (sigdelayed (x86_64)): Save and restore FPU control word.")
Reported-by: Christian Franke <Christian.Franke@t-online.de>
Suggested-by: Brian Inglis <Brian.Inglis@SystematicSW.ab.ca>
Reviewed-by: Corinna Vinschen <corinna@vinschen.de>
Signed-off-by: Takashi Yano <takashi.yano@nifty.ne.jp>
