tree 397479a3271a09dfae0be95e9661cb2f6be5237d
parent b9297dcdf2a380a3677307d0ac77983dc0e6a199
author Hans Wennborg <hans@chromium.org> 1574866064 +0100
committer Tom Stellard <tstellar@redhat.com> 1575564691 -0800

[profile] Fix file contention causing dropped counts on Windows under -fprofile-generate

See PR43425:
https://bugs.llvm.org/show_bug.cgi?id=43425

When writing profile data on Windows we were opening profile file with
exclusive read/write access.

In case we are trying to write to the file from multiple processes
simultaneously, subsequent calls to CreateFileA would return
INVALID_HANDLE_VALUE.

To fix this, I changed to open without exclusive access and then take a
lock.

Patch by Michael Holman!

Differential revision: https://reviews.llvm.org/D70330

(cherry picked from commit 900d8a9a3b4efeefddd310e92219741d98e7270b)