• Austin Clements's avatar
    runtime: always call stackfree on the system stack · 6a86dbe7
    Austin Clements authored
    Currently when the garbage collector frees stacks of dead goroutines
    in markrootFreeGStacks, it calls stackfree on a regular user stack.
    This is a problem, since stackfree manipulates the stack cache in the
    per-P mcache, so if it grows the stack or gets preempted in the middle
    of manipulating the stack cache (which are both possible since it's on
    a user stack), it can easily corrupt the stack cache.
    
    Fix this by calling markrootFreeGStacks on the system stack, so that
    all calls to stackfree happen on the system stack. To prevent this bug
    in the future, mark stack functions that manipulate the mcache as
    go:systemstack.
    
    Fixes #15853.
    
    Change-Id: Ic0d1c181efb342f134285a152560c3a074f14a3d
    Reviewed-on: https://go-review.googlesource.com/23511
    Run-TryBot: Austin Clements <austin@google.com>
    Reviewed-by: default avatarKeith Randall <khr@golang.org>
    Reviewed-by: default avatarRick Hudson <rlh@golang.org>
    TryBot-Result: Gobot Gobot <gobot@golang.org>
    6a86dbe7
mgcmark.go 39.8 KB