• Austin Clements's avatar
    runtime: prevent sigprof during all stack barrier ops · 9c9d74ab
    Austin Clements authored
    A sigprof during stack barrier insertion or removal can crash if it
    detects an inconsistency between the stkbar array and the stack
    itself. Currently we protect against this when scanning another G's
    stack using stackLock, but we don't protect against it when unwinding
    stack barriers for a recover or a memmove to the stack.
    
    This commit cleans up and improves the stack locking code. It
    abstracts out the lock and unlock operations. It uses the lock
    consistently everywhere we perform stack operations, and pushes the
    lock/unlock down closer to where the stack barrier operations happen
    to make it more obvious what it's protecting. Finally, it modifies
    sigprof so that instead of spinning until it acquires the lock, it
    simply doesn't perform a traceback if it can't acquire it. This is
    necessary to prevent self-deadlock.
    
    Updates #11863, which introduced stackLock to fix some of these
    issues, but didn't go far enough.
    
    Updates #12528.
    
    Change-Id: I9d1fa88ae3744d31ba91500c96c6988ce1a3a349
    Reviewed-on: https://go-review.googlesource.com/17036Reviewed-by: 's avatarRuss Cox <rsc@golang.org>
    Run-TryBot: Austin Clements <austin@google.com>
    TryBot-Result: Gobot Gobot <gobot@golang.org>
    9c9d74ab
mstkbar.go 11.5 KB