Re: [PATCH v3] libiberty: Use posix_spawn in pex-unix when available.

[Patrick O'Neill <patrick@rivosinc.com>]

[-- Attachment #1: Type: text/plain, Size: 10230 bytes --]

On 11/10/23 03:00, Prathamesh Kulkarni wrote:

> On Thu, 5 Oct 2023 at 00:00, Brendan Shanks<bshanks@codeweavers.com>  wrote:
>> Hi,
>>
>> This patch implements pex_unix_exec_child using posix_spawn when
>> available.
>>
>> This should especially benefit recent macOS (where vfork just calls
>> fork), but should have equivalent or faster performance on all
>> platforms.
>> In addition, the implementation is substantially simpler than the
>> vfork+exec code path.
>>
>> Tested on x86_64-linux.
> Hi Brendan,
> It seems this patch caused the following regressions on aarch64:

I'm also seeing the same failures on risc-v targets bisected to this commit.

Thanks,
Patrick

>
> FAIL: g++.dg/modules/bad-mapper-1.C -std=c++17  at line 3 (test for
> errors, line )
> FAIL: g++.dg/modules/bad-mapper-1.C -std=c++17 (test for excess errors)
> FAIL: g++.dg/modules/bad-mapper-1.C -std=c++2a  at line 3 (test for
> errors, line )
> FAIL: g++.dg/modules/bad-mapper-1.C -std=c++2a (test for excess errors)
> FAIL: g++.dg/modules/bad-mapper-1.C -std=c++2b  at line 3 (test for
> errors, line )
> FAIL: g++.dg/modules/bad-mapper-1.C -std=c++2b (test for excess errors)
>
> Looking at g++.log:
> /home/tcwg-buildslave/workspace/tcwg_gnu_2/abe/snapshots/gcc.git~master/gcc/testsuite/g++.dg/modules/bad-mapper-1.C:
> error: failed posix_spawnp mapper 'this-will-not-work'
> In module imported at
> /home/tcwg-buildslave/workspace/tcwg_gnu_2/abe/snapshots/gcc.git~master/gcc/testsuite/g++.dg/modules/bad-mapper-1.C:2:1:
> unique1.bob: error: failed to read compiled module: No such file or directory
> unique1.bob: note: compiled module file is 'gcm.cache/unique1.bob.gcm'
> unique1.bob: note: imports must be built before being imported
> unique1.bob: fatal error: returning to the gate for a mechanical issue
> compilation terminated.
>
> Link to log files:
> https://ci.linaro.org/job/tcwg_gcc_check--master-aarch64-build/1159/artifact/artifacts/00-sumfiles/
> Could you please investigate ?
>
> Thanks,
> Prathamesh
>> v2: Fix error handling (previously the function would be run twice in
>> case of error), and don't use a macro that changes control flow.
>>
>> v3: Match file style for error-handling blocks, don't close
>> in/out/errdes on error, and check close() for errors.
>>
>> libiberty/
>>          * configure.ac (AC_CHECK_HEADERS): Add spawn.h.
>>          (checkfuncs): Add posix_spawn, posix_spawnp.
>>          (AC_CHECK_FUNCS): Add posix_spawn, posix_spawnp.
>>          * configure, config.in: Rebuild.
>>          * pex-unix.c [HAVE_POSIX_SPAWN] (pex_unix_exec_child): New function.
>>
>> Signed-off-by: Brendan Shanks<bshanks@codeweavers.com>
>> ---
>>   libiberty/configure.ac |   8 +-
>>   libiberty/pex-unix.c   | 168 +++++++++++++++++++++++++++++++++++++++++
>>   2 files changed, 173 insertions(+), 3 deletions(-)
>>
>> diff --git a/libiberty/configure.ac b/libiberty/configure.ac
>> index 0748c592704..2488b031bc8 100644
>> --- a/libiberty/configure.ac
>> +++ b/libiberty/configure.ac
>> @@ -289,7 +289,7 @@ AC_SUBST_FILE(host_makefile_frag)
>>   # It's OK to check for header files.  Although the compiler may not be
>>   # able to link anything, it had better be able to at least compile
>>   # something.
>> -AC_CHECK_HEADERS(sys/file.h sys/param.h limits.h stdlib.h malloc.h string.h unistd.h strings.h sys/time.h time.h sys/resource.h sys/stat.h sys/mman.h fcntl.h alloca.h sys/pstat.h sys/sysmp.h sys/sysinfo.h machine/hal_sysinfo.h sys/table.h sys/sysctl.h sys/systemcfg.h stdint.h stdio_ext.h process.h sys/prctl.h)
>> +AC_CHECK_HEADERS(sys/file.h sys/param.h limits.h stdlib.h malloc.h string.h unistd.h strings.h sys/time.h time.h sys/resource.h sys/stat.h sys/mman.h fcntl.h alloca.h sys/pstat.h sys/sysmp.h sys/sysinfo.h machine/hal_sysinfo.h sys/table.h sys/sysctl.h sys/systemcfg.h stdint.h stdio_ext.h process.h sys/prctl.h spawn.h)
>>   AC_HEADER_SYS_WAIT
>>   AC_HEADER_TIME
>>
>> @@ -412,7 +412,8 @@ funcs="$funcs setproctitle"
>>   vars="sys_errlist sys_nerr sys_siglist"
>>
>>   checkfuncs="__fsetlocking canonicalize_file_name dup3 getrlimit getrusage \
>> - getsysinfo gettimeofday on_exit pipe2 psignal pstat_getdynamic pstat_getstatic \
>> + getsysinfo gettimeofday on_exit pipe2 posix_spawn posix_spawnp psignal \
>> + pstat_getdynamic pstat_getstatic \
>>    realpath setrlimit spawnve spawnvpe strerror strsignal sysconf sysctl \
>>    sysmp table times wait3 wait4"
>>
>> @@ -435,7 +436,8 @@ if test "x" = "y"; then
>>       index insque \
>>       memchr memcmp memcpy memmem memmove memset mkstemps \
>>       on_exit \
>> -    pipe2 psignal pstat_getdynamic pstat_getstatic putenv \
>> +    pipe2 posix_spawn posix_spawnp psignal \
>> +    pstat_getdynamic pstat_getstatic putenv \
>>       random realpath rename rindex \
>>       sbrk setenv setproctitle setrlimit sigsetmask snprintf spawnve spawnvpe \
>>        stpcpy stpncpy strcasecmp strchr strdup \
>> diff --git a/libiberty/pex-unix.c b/libiberty/pex-unix.c
>> index 33b5bce31c2..336799d1125 100644
>> --- a/libiberty/pex-unix.c
>> +++ b/libiberty/pex-unix.c
>> @@ -58,6 +58,9 @@ extern int errno;
>>   #ifdef HAVE_PROCESS_H
>>   #include <process.h>
>>   #endif
>> +#ifdef HAVE_SPAWN_H
>> +#include <spawn.h>
>> +#endif
>>
>>   #ifdef vfork /* Autoconf may define this to fork for us. */
>>   # define VFORK_STRING "fork"
>> @@ -559,6 +562,171 @@ pex_unix_exec_child (struct pex_obj *obj ATTRIBUTE_UNUSED,
>>     return (pid_t) -1;
>>   }
>>
>> +#elif defined(HAVE_POSIX_SPAWN) && defined(HAVE_POSIX_SPAWNP)
>> +/* Implementation of pex->exec_child using posix_spawn.            */
>> +
>> +static pid_t
>> +pex_unix_exec_child (struct pex_obj *obj ATTRIBUTE_UNUSED,
>> +                    int flags, const char *executable,
>> +                    char * const * argv, char * const * env,
>> +                    int in, int out, int errdes,
>> +                    int toclose, const char **errmsg, int *err)
>> +{
>> +  int ret;
>> +  pid_t pid = -1;
>> +  posix_spawnattr_t attr;
>> +  posix_spawn_file_actions_t actions;
>> +  int attr_initialized = 0, actions_initialized = 0;
>> +
>> +  *err = 0;
>> +
>> +  ret = posix_spawnattr_init (&attr);
>> +  if (ret)
>> +    {
>> +      *err = ret;
>> +      *errmsg = "posix_spawnattr_init";
>> +      goto exit;
>> +    }
>> +  attr_initialized = 1;
>> +
>> +  /* Use vfork() on glibc <=2.24. */
>> +#ifdef POSIX_SPAWN_USEVFORK
>> +  ret = posix_spawnattr_setflags (&attr, POSIX_SPAWN_USEVFORK);
>> +  if (ret)
>> +    {
>> +      *err = ret;
>> +      *errmsg = "posix_spawnattr_setflags";
>> +      goto exit;
>> +    }
>> +#endif
>> +
>> +  ret = posix_spawn_file_actions_init (&actions);
>> +  if (ret)
>> +    {
>> +      *err = ret;
>> +      *errmsg = "posix_spawn_file_actions_init";
>> +      goto exit;
>> +    }
>> +  actions_initialized = 1;
>> +
>> +  if (in != STDIN_FILE_NO)
>> +    {
>> +      ret = posix_spawn_file_actions_adddup2 (&actions, in, STDIN_FILE_NO);
>> +      if (ret)
>> +        {
>> +          *err = ret;
>> +          *errmsg = "posix_spawn_file_actions_adddup2";
>> +          goto exit;
>> +        }
>> +
>> +      ret = posix_spawn_file_actions_addclose (&actions, in);
>> +      if (ret)
>> +        {
>> +          *err = ret;
>> +          *errmsg = "posix_spawn_file_actions_addclose";
>> +          goto exit;
>> +        }
>> +    }
>> +
>> +  if (out != STDOUT_FILE_NO)
>> +    {
>> +      ret = posix_spawn_file_actions_adddup2 (&actions, out, STDOUT_FILE_NO);
>> +      if (ret)
>> +        {
>> +          *err = ret;
>> +          *errmsg = "posix_spawn_file_actions_adddup2";
>> +          goto exit;
>> +        }
>> +
>> +      ret = posix_spawn_file_actions_addclose (&actions, out);
>> +      if (ret)
>> +        {
>> +          *err = ret;
>> +          *errmsg = "posix_spawn_file_actions_addclose";
>> +          goto exit;
>> +        }
>> +    }
>> +
>> +  if (errdes != STDERR_FILE_NO)
>> +    {
>> +      ret = posix_spawn_file_actions_adddup2 (&actions, errdes, STDERR_FILE_NO);
>> +      if (ret)
>> +        {
>> +          *err = ret;
>> +          *errmsg = "posix_spawn_file_actions_adddup2";
>> +          goto exit;
>> +        }
>> +
>> +      ret = posix_spawn_file_actions_addclose (&actions, errdes);
>> +      if (ret)
>> +        {
>> +          *err = ret;
>> +          *errmsg = "posix_spawn_file_actions_addclose";
>> +          goto exit;
>> +        }
>> +    }
>> +
>> +  if (toclose >= 0)
>> +    {
>> +      ret = posix_spawn_file_actions_addclose (&actions, toclose);
>> +      if (ret)
>> +        {
>> +          *err = ret;
>> +          *errmsg = "posix_spawn_file_actions_addclose";
>> +          goto exit;
>> +        }
>> +    }
>> +
>> +  if ((flags & PEX_STDERR_TO_STDOUT) != 0)
>> +    {
>> +      ret = posix_spawn_file_actions_adddup2 (&actions, STDOUT_FILE_NO, STDERR_FILE_NO);
>> +      if (ret)
>> +        {
>> +          *err = ret;
>> +          *errmsg = "posix_spawn_file_actions_adddup2";
>> +          goto exit;
>> +        }
>> +    }
>> +
>> +  if ((flags & PEX_SEARCH) != 0)
>> +    {
>> +      ret = posix_spawnp (&pid, executable, &actions, &attr, argv, env ? env : environ);
>> +      if (ret)
>> +        {
>> +          *err = ret;
>> +          *errmsg = "posix_spawnp";
>> +          goto exit;
>> +        }
>> +    }
>> +  else
>> +    {
>> +      ret = posix_spawn (&pid, executable, &actions, &attr, argv, env ? env : environ);
>> +      if (ret)
>> +        {
>> +          *err = ret;
>> +          *errmsg = "posix_spawn";
>> +          goto exit;
>> +        }
>> +    }
>> +
>> +exit:
>> +  if (actions_initialized)
>> +    posix_spawn_file_actions_destroy (&actions);
>> +  if (attr_initialized)
>> +    posix_spawnattr_destroy (&attr);
>> +
>> +  if (!*err && in != STDIN_FILE_NO)
>> +    if (close (in))
>> +      *errmsg = "close", *err = errno, pid = -1;
>> +  if (!*err && out != STDOUT_FILE_NO)
>> +    if (close (out))
>> +      *errmsg = "close", *err = errno, pid = -1;
>> +  if (!*err && errdes != STDERR_FILE_NO)
>> +    if (close (errdes))
>> +      *errmsg = "close", *err = errno, pid = -1;
>> +
>> +  return pid;
>> +}
>>   #else
>>   /* Implementation of pex->exec_child using standard vfork + exec.  */
>>
>> --
>> 2.41.0
>>