Hi,
Il 13/01/26 19:19, Samuel Thibault ha scritto:
Hello,
The haskell packages builds have shown that we still have unexpected xmm
clobbers on signals/interrupt or such on x86_64.
Do you think it might be related to some gcc optimization? IIRC the
current strategy is not very robust as it assumes some parts of signal
handling in libc don't use xmm registers.
This can be seen notably with package haskell-src-exts:
https://buildd.debian.org/status/logs.php?pkg=haskell-src-exts&arch=hurd-amd64
we have more than two dozen failures trying to build it, giving
waitForProcess: failed ((ipc/mig) server type check failure)
That's with libc0.3_2.42-8~hurd.1, and as soon as I updated to
libc0.3_2.42-8~hurd.2, it built fine. The only difference between these
two libcs is
Index: glibc-2.38/hurd/intr-msg.c
===================================================================
--- glibc-2.38.orig/hurd/intr-msg.c
+++ glibc-2.38/hurd/intr-msg.c
@@ -79,7 +79,7 @@ _hurd_intr_rpc_mach_msg (mach_msg_header
mach_msg_bits_t msgh_bits;
mach_port_t remote_port;
mach_msg_id_t msgid;
- struct clobber save_data;
+ volatile struct clobber save_data;
if ((option & (MACH_SEND_MSG|MACH_RCV_MSG)) != (MACH_SEND_MSG|MACH_RCV_MSG)
|| _hurd_msgport_thread == MACH_PORT_NULL)
which makes sure to put the content of save_data on the stack instead of
in xmm0, while calling mach_msg().
So we have something that clobbers xmm0 somehow, and this is only a dumb
workaround that only avoids the issue in the notable but still
particular case of blocking RPCs.
We do have a basic test against signals, hurd/test-sig-xstate.c, but
apparently it's not stressful enough.
haskell is a bit particular compared to other packages because it
has a preemption SIGVTALRM signal happening periodically, which is
most probably the trigger for the issue. Notably, during the ghc
package build, I have to use GHCRTS=-V0 to disable it, otherwise I'm
seeing corruptions. The haskell packages builds occasionally see such
corruptions too.
Does this mean that even with the change above the ghc build fails,
unless GHCRTS=-V0 is used?
Luca
