Commit 432bf48c authored by Hans Wennborg's avatar Hans Wennborg Committed by Tom Stellard
Browse files

[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 900d8a9a)
parent b9297dcd

compiler-rt/lib/profile/InstrProfilingUtil.c

+7 −2
Original line number Diff line number Diff line
@@ -189,8 +189,9 @@ COMPILER_RT_VISIBILITY FILE *lprofOpenFileEx(const char *ProfileName) { 
  f = fdopen(fd, "r+b");

#elif defined(_WIN32)

  // FIXME: Use the wide variants to handle Unicode filenames.

  HANDLE h = CreateFileA(ProfileName, GENERIC_READ | GENERIC_WRITE, 0, 0,

                         OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, 0);

  HANDLE h = CreateFileA(ProfileName, GENERIC_READ | GENERIC_WRITE,

                         FILE_SHARE_READ | FILE_SHARE_WRITE, 0, OPEN_ALWAYS,

                         FILE_ATTRIBUTE_NORMAL, 0);

  if (h == INVALID_HANDLE_VALUE)

    return NULL;
@@ -200,6 +201,10 @@ COMPILER_RT_VISIBILITY FILE *lprofOpenFileEx(const char *ProfileName) { 
    return NULL;

  }



  if (lprofLockFd(fd) != 0)

    PROF_WARN("Data may be corrupted during profile merging : %s\n",

              "Fail to obtain file lock due to system limit.");



  f = _fdopen(fd, "r+b");

  if (f == 0) {

    CloseHandle(h);

compiler-rt/test/profile/Windows/Inputs/instrprof-multiprocess.c

0 → 100644
+89 −0
Original line number Diff line number Diff line 
/* This is a test case where the parent process forks 10 children

 * which contend to merge profile data to the same file. With

 * file locking support, the data from each child should not

 * be lost.

 */

#include <stdio.h>

#include <stdlib.h>

#include <windows.h>



void spawn_child(PROCESS_INFORMATION *pi, int child_num) {

  wchar_t child_str[10];

  _itow(child_num, child_str, 10);

  if (!SetEnvironmentVariableW(L"CHILD_NUM", child_str)) {

    printf("SetEnvironmentVariableW failed (0x%8lx).\n", GetLastError());

    fflush(stdout);

    exit(1);

  }



  STARTUPINFOW si;

  memset(&si, 0, sizeof(si));

  si.cb = sizeof(si);



  memset(pi, 0, sizeof(PROCESS_INFORMATION));



  if (!CreateProcessW(NULL,              // No module name (use command line)

                      GetCommandLineW(), // Command line

                      NULL,              // Process handle not inheritable

                      NULL,              // Thread handle not inheritable

                      TRUE,              // Set handle inheritance to TRUE

                      0,                 // No flags

                      NULL,              // Use parent's environment block

                      NULL,              // Use parent's starting directory

                      &si, pi)) {

    printf("CreateProcess failed (0x%08lx).\n", GetLastError());

    fflush(stdout);

    exit(1);

  }

}



int wait_child(PROCESS_INFORMATION *pi) {

  WaitForSingleObject(pi->hProcess, INFINITE);



  DWORD exit_code;

  if (!GetExitCodeProcess(pi->hProcess, &exit_code)) {

    printf("GetExitCodeProcess failed (0x%08lx).\n", GetLastError());

    fflush(stdout);

    exit(1);

  }



  CloseHandle(pi->hProcess);

  CloseHandle(pi->hThread);



  return exit_code;

}



#define NUM_CHILDREN 10



int foo(int num) {

  if (num < (NUM_CHILDREN / 2)) {

    return 1;

  } else if (num < NUM_CHILDREN) {

    return 2;

  }

  return 3;

}



int main(int argc, char *argv[]) {

  char *child_str = getenv("CHILD_NUM");

  if (!child_str) {

    PROCESS_INFORMATION child[NUM_CHILDREN];

    // In parent

    for (int i = 0; i < NUM_CHILDREN; i++) {

      spawn_child(&child[i], i);

    }

    for (int i = 0; i < NUM_CHILDREN; i++) {

      wait_child(&child[i]);

    }

    return 0;

  } else {

    // In child

    int child_num = atoi(child_str);

    int result = foo(child_num);

    if (result == 3) {

      fprintf(stderr, "Invalid child count!");

      return 1;

    }

    return 0;

  }

}

compiler-rt/test/profile/Windows/instrprof-multiprocess.test

0 → 100644
+10 −0
Original line number Diff line number Diff line 
RUN: %clang_profgen %S/Inputs/instrprof-multiprocess.c -o %t

RUN: rm -f %t_*.profraw

RUN: env LLVM_PROFILE_FILE=%t_%m.profraw %run %t

RUN: llvm-profdata show --counts -function=foo %t_*.profraw | FileCheck %s



CHECK: Counters:

CHECK:   foo:

CHECK:     Function count: 10

CHECK:     Block counts: [5, 5]

CHECK: Functions shown: 1

compiler-rt/test/profile/Windows/lit.local.cfg.py

0 → 100644
+9 −0
Original line number Diff line number Diff line 
def getRoot(config):

  if not config.parent:

    return config

  return getRoot(config.parent)



root = getRoot(config)



if root.host_os not in ['Windows']:

  config.unsupported = True