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author | Ian Lance Taylor <ian@gcc.gnu.org> | 2017-06-23 16:05:44 +0000 |
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committer | Ian Lance Taylor <ian@gcc.gnu.org> | 2017-06-23 16:05:44 +0000 |
commit | bb96aa6726d1fac7e2500ef37d1193eed00b03f1 (patch) | |
tree | f9c9927c7f70e3dd316f3234661634304e55c10a /libgo/go | |
parent | 5f0b897b2ee47bf3845d924dd5bc3beb949bc78b (diff) | |
download | gcc-bb96aa6726d1fac7e2500ef37d1193eed00b03f1.zip gcc-bb96aa6726d1fac7e2500ef37d1193eed00b03f1.tar.gz gcc-bb96aa6726d1fac7e2500ef37d1193eed00b03f1.tar.bz2 |
runtime: don't crash if no p in kickoff
The kickoff function for g0 can be invoked without a p, for example
from mcall(exitsyscall0) in exitsyscall after exitsyscall has cleared
the p field. The assignment gp.param = nil will invoke a write barrier.
If gp.param is not already nil, this will require a p. Avoid the problem
for a specific case that is known to be OK: when the value in gp.param
is a *g.
Reviewed-on: https://go-review.googlesource.com/46512
From-SVN: r249595
Diffstat (limited to 'libgo/go')
-rw-r--r-- | libgo/go/runtime/proc.go | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/libgo/go/runtime/proc.go b/libgo/go/runtime/proc.go index 77b624b..6b6f9c9 100644 --- a/libgo/go/runtime/proc.go +++ b/libgo/go/runtime/proc.go @@ -1097,7 +1097,25 @@ func kickoff() { fv := gp.entry param := gp.param gp.entry = nil + + // When running on the g0 stack we can wind up here without a p, + // for example from mcall(exitsyscall0) in exitsyscall. + // Setting gp.param = nil will call a write barrier, and if + // there is no p that write barrier will crash. When called from + // mcall the gp.param value will be a *g, which we don't need to + // shade since we know it will be kept alive elsewhere. In that + // case clear the field using uintptr so that the write barrier + // does nothing. + if gp.m.p == 0 { + if gp == gp.m.g0 && gp.param == unsafe.Pointer(gp.m.curg) { + *(*uintptr)(unsafe.Pointer(&gp.param)) = 0 + } else { + throw("no p in kickoff") + } + } + gp.param = nil + fv(param) goexit1() } |