runtime: fix fault during arm software floating point
The software floating point runs with m->locks++
to avoid being preempted; recognize this case in panic
and undo it so that m->locks is maintained correctly
when panicking.
Fixes #7553.
LGTM=dvyukov
R=golang-codereviews, dvyukov
CC=golang-codereviews
https://golang.org/cl/84030043
diff --git a/src/pkg/runtime/panic.c b/src/pkg/runtime/panic.c
index 0bf3b6a..3af8cb6 100644
--- a/src/pkg/runtime/panic.c
+++ b/src/pkg/runtime/panic.c
@@ -498,7 +498,7 @@
// and not stuck in a system call.
if(gp == nil || gp != m->curg)
return false;
- if(m->locks != 0 || m->mallocing != 0 || m->throwing != 0 || m->gcing != 0 || m->dying != 0)
+ if(m->locks-m->softfloat != 0 || m->mallocing != 0 || m->throwing != 0 || m->gcing != 0 || m->dying != 0)
return false;
if(gp->status != Grunning || gp->syscallsp != 0)
return false;
@@ -526,6 +526,16 @@
{
Eface err;
+ // m->softfloat is set during software floating point,
+ // which might cause a fault during a memory load.
+ // It increments m->locks to avoid preemption.
+ // If we're panicking, the software floating point frames
+ // will be unwound, so decrement m->locks as they would.
+ if(m->softfloat) {
+ m->locks--;
+ m->softfloat = 0;
+ }
+
if(m->mallocing) {
runtime·printf("panic: %s\n", s);
runtime·throw("panic during malloc");
@@ -534,6 +544,10 @@
runtime·printf("panic: %s\n", s);
runtime·throw("panic during gc");
}
+ if(m->locks) {
+ runtime·printf("panic: %s\n", s);
+ runtime·throw("panic holding locks");
+ }
runtime·newErrorCString(s, &err);
runtime·panic(err);
}
diff --git a/src/pkg/runtime/runtime.h b/src/pkg/runtime/runtime.h
index 28c831a0..0ba1238 100644
--- a/src/pkg/runtime/runtime.h
+++ b/src/pkg/runtime/runtime.h
@@ -312,6 +312,7 @@
int32 throwing;
int32 gcing;
int32 locks;
+ int32 softfloat;
int32 dying;
int32 profilehz;
int32 helpgc;
diff --git a/src/pkg/runtime/vlop_arm.s b/src/pkg/runtime/vlop_arm.s
index 941de3e..80f516e 100644
--- a/src/pkg/runtime/vlop_arm.s
+++ b/src/pkg/runtime/vlop_arm.s
@@ -75,10 +75,14 @@
MOVW m_locks(m), R1
ADD $1, R1
MOVW R1, m_locks(m)
+ MOVW $1, R1
+ MOVW R1, m_softfloat(m)
BL runtime·_sfloat2(SB)
MOVW m_locks(m), R1
SUB $1, R1
MOVW R1, m_locks(m)
+ MOVW $0, R1
+ MOVW R1, m_softfloat(m)
MOVW R0, 0(R13)
MOVW 64(R13), R1
WORD $0xe128f001 // msr cpsr_f, r1
