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This improves the latency of file operations as dirty schedulers
are a bit more eager to run jobs than async threads, and use a
single global queue rather than per-thread queues, eliminating the
risk of a job stalling behind a long-running job on the same thread
while other async threads sit idle.
There's no such thing as a free lunch though; the lowered latency
comes at the cost of increased busy-waiting which may have an
adverse effect on some applications. This behavior can be tweaked
with the +sbwt flag, but unfortunately it affects all types of
schedulers and not just dirty ones. We plan to add type-specific
flags at a later stage.
sendfile has been moved to inet_drv to lessen the effect of a nasty
race; the cooperation between inet_drv and efile has never been
airtight and the socket dying at the wrong time (Regardless of
reason) could result in fd aliasing. Moving it to the inet driver
makes it impossible to trigger this by closing the socket in the
middle of a sendfile operation, while still allowing it to be
aborted -- something that can't be done if it stays in the file
driver.
The race still occurs if the controlling process dies in the short
window between dispatching the sendfile operation and the dup(2)
call in the driver, but it's much less likely to happen now.
A proper fix is in the works.
--
Notable functional differences:
* The use_threads option for file:sendfile/5 no longer has any
effect.
* The file-specific DTrace probes have been removed. The same
effect can be achieved with normal tracing together with the
nif__entry/nif__return probes to track scheduling.
--
OTP-14256
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This is mostly a pure refactoring.
Except for the buggy cases when calling erlang:halt() with a positive
integer in the range -(INT_MIN+2) to -INT_MIN that got confused with
ERTS_ABORT_EXIT, ERTS_DUMP_EXIT and ERTS_INTR_EXIT.
Outcome OLD erl_exit(n, ) NEW erts_exit(n, )
------- ------------------- -------------------------------------------
exit(Status) n = -Status <= 0 n = Status >= 0
crashdump+abort n > 0, ignore n n = ERTS_ERROR_EXIT < 0
The outcome of the old ERTS_ABORT_EXIT, ERTS_INTR_EXIT and
ERTS_DUMP_EXIT are the same as before (even though their values have
changed).
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* maint:
erts: Initialize links when reading file info
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Added a put_chars_sync to the protocol that can be used to
talk to user_drv and made group use it. This is needed in order
to guarantee that bytes has been pushed to the tty port when
doing something like this:
io:format("halting\n"),erlang:halt(0).
Before this change the halting message could be lost in the message
queue of the user_drv process, this is no longer possible.
This commit also fixes ssh_cli as that plugs itself in as a user_drv
process.
OTP-12240
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* sverk/win-long-filenames/OTP-11813:
erts: Cleanup debug tracing in win_efile.c
erts: Fix file:list_dir for windows paths 258 or 259 chars long
erts: Increase MAXPATHLEN to 4096 for windows
erts: Fix bug in efile_readlink for long win paths
kernel: Fix failed tests in prim_file_SUITE for windows
erts: Fix compiler warning in win_efile.c
erts: Skip tests of paths longer than 255 characters as atoms
erts: Skip tests of file:set_cwd for too long path on Windows
erts: Make file:make_symlink/2 return {error,eperm} on Windows
erts: Revert file:set_cwd impl for windows
erts: Ignore reduntant slashes in windows paths
fix file_SUITE:cur_dir_0 for long windows paths
erts: Fix file_SUITE:make_del_dir for long paths
erts: Fix long windows paths for compressed files
erts: Use GetFullPathNameW to construct abs paths from relative ones
erts: Fix file driver to handle long paths on windows
Conflicts:
erts/emulator/drivers/win32/win_efile.c
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Appending wildcard "\*" made the path too long (>= 260 chars).
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and some improved debug tracing
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if the user has not the privilege SE_CREATE_SYMBOLIC_LINK_NAME
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No need to even try as CWD can not bee a long path anyway.
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The sync option adds the POSIX O_SYNC flag to the open system call on
platforms that support the flag or its equivalent, e.g.,
FILE_FLAG_WRITE_THROUGH on Windows. For platforms that don't support it,
file:open/2 returns {error, enotsup} if the sync option is passed in.
The semantics of O_SYNC are platform-specific. For example, not all
platforms guarantee that all file metadata are written to the disk along
with the file data when the flag is in effect. This issue is noted in the
documentation this commit adds for the sync option.
Add a test for the sync option. Note however that the underlying OS
semantics for O_SYNC can't be tested automatically in any practical way, so
the test assumes the OS does the right thing with the flag when
present. For manual verification, dtruss on OS X and strace on Linux were
both run against beam processes to watch calls to open(), and file:open/2
was called in Erlang shells to open files for writing, both with and
without the sync option. Both the dtruss output and the strace output
showed that the O_SYNC flag was present in the open() calls when sync was
specified and was clear when sync was not specified.
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files as delimiters.
While working on a tool that processes Erlang code and testing it against this repo,
I found out about those little sneaky 0xff. I thought it may be of help to other
people build such tools to remove non-conforming-to-standard characters.
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Using a 64bit type for bytes read will not always clear the higher bits.
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Some file operations provided by the Erlang file module
didn't open the target file with all the file share flags.
This made some concurrent file operations against the
same file fail on Windows, while on other platforms such
as GNU/Linux or Mac OS X they succeed. The operations will
fail only if they're performed concurrently by different
threads (async IO threads or scheduler threads).
For example, one Erlang process does a file:delete/1 call
while another Erlang process is doing a filelib:file_size/1
call. This made the former process get an eacces error from
the file:delete/1 call. On GNU/Linux or Mac OS X the call would
succeed. Another example is if one Erlang process attempts to
open a file for reading while another one is in the middle of
a file:read_file_info/1 call (after it opened the file and
before it closed the file).
It's easy to verify that if a file is not open with all the
share flags, it's impossible for other threads (even if they
belong to the same OS process) to open the file while the
file is not closed by the first thread.
The following test program shows this:
#include <windows.h>
#include <iostream>
// Must be an existing file
//#define SHARE_FLAGS (FILE_SHARE_READ)
static DWORD WINAPI MyThreadFunction(LPVOID lpParam);
static char *lastError();
int main(int argc, char *argv[])
{
DWORD threadId;
HANDLE threadHandle, hFile;
hFile = CreateFile(FILENAME, GENERIC_READ, SHARE_FLAGS, NULL,
OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
if (hFile == INVALID_HANDLE_VALUE) {
std::cerr << "File open error from main: " <<
lastError() << std::endl;
return 1;
}
std::cout << "Main thread opened file successfully" << std::endl;
threadHandle = CreateThread(NULL, 0, MyThreadFunction, NULL, 0, &threadId);
if (threadHandle == INVALID_HANDLE_VALUE) {
std::cerr << "Thread create error from main: " <<
lastError() << std::endl;
return 1;
}
WaitForSingleObject(threadHandle, INFINITE);
CloseHandle(threadHandle);
CloseHandle(hFile);
return 0;
}
static DWORD WINAPI MyThreadFunction( LPVOID lpParam )
{
HANDLE hFile;
hFile = CreateFile(FILENAME, GENERIC_READ, SHARE_FLAGS, NULL,
OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
if (hFile == INVALID_HANDLE_VALUE) {
std::cerr << "File open error from second thread: " <<
lastError() << std::endl;
return 1;
}
std::cout << "Second thread opened file successfully" << std::endl;
CloseHandle(hFile);
return 0;
}
static char *lastError()
{
static char *buf = NULL;
DWORD dw = GetLastError();
if (buf != NULL) {
LocalFree((LPTSTR) &buf);
}
FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM |
FORMAT_MESSAGE_IGNORE_INSERTS,
NULL, dw, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
(LPTSTR) &buf, 0, NULL);
return buf;
}
Rnning this program with SHARE_FLAGS set to 0 (as efile_fileinfo()
does for e.g.), shows that the second thread is unable to open the
file:
C:\cygwin\home\fdmanana\tmp>touch foo.bar
C:\cygwin\home\fdmanana\tmp>threads_fopen_test.exe
Main thread opened file successfully
File open error from second thread: The process cannot access the
file because it is being used by another process.
Changing the program's SHARE_FLAGS to FILE_SHARE_READ, shows that
both threads are able to open the file:
C:\cygwin\home\fdmanana\tmp>touch foo.bar
C:\cygwin\home\fdmanana\tmp>threads_test.exe
Main thread opened file successfully
Second thread opened file successfully
Same logic applies to opening files for writing or deleting and
renaming files while they're open by some other thread that didn't
specify the flags FILE_SHARE_WRITE and FILE_SHARE_DELETE.
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This operation allows pre-allocation of space for files.
It succeeds only on systems that support such operation.
The POSIX standard defines the optional system call
posix_fallocate() to implement this feature. However,
some systems implement more specific functions to
accomplish the same operation.
On Linux, if the more specific function fallocate() is
implemented, it is used instead of posix_fallocate(),
falling back to posix_fallocate() if the fallocate()
call failed (it's only supported for the ext4, ocfs2,
xfs and btrfs file systems at the moment).
On Mac OS X it uses the specific fcntl() operation
F_PREALLOCATE, falling back to posix_fallocate() if
it's available (at the moment Mac OS X doesn't provide
posix_fallocate()).
On any other UNIX system, it uses posix_fallocate() if it's
available. Any other system not providing this system call
or any function to pre-allocate space for files, this operation
always fails with the ENOTSUP POSIX error.
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Long input paths (longer than MAX_PATH) would get copied
into a buffer of size MAX_PATH for read_link and altname
in efile_drv.
Also fixed misuse of size_t parameter as wchar_t *
string length in win_efile:efile_readlink.
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Incorrect window was used to calculate x position.
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* raimo/64-bit-driver-api/OTP-9795: (22 commits)
driver_SUITE.erl: Fix sys info drivers
emulator test drivers: Conform to updated driver API
runtime_tools's drivers: Conform to updated driver API
ws's xwe_driver.c: Conform to updated driver API
megaco's flex scanner: Conform to updated driver API
seq_trace_SUITE_data/echo_drv.c: Conform to updated driver API
erl_interface tests: Conform port_call_drv.c updated driver API
erl_drv_thread_SUITE_data/testcase_driver.c: Conform to updated driver API
float_SUITE_data/fp_drv.c: Conform to updated driver API
port_SUITE_data/*_drv.c: Conform to updated driver API
port_bif_SUITE_data/control_drv.c: Conform to updated driver API
send_term_SUITE_data/send_term_drv.c: Conform to updated driver API
system_profile_SUITE_data/echo_drv.c: Conform to updated driver API
trace_port_SUITE_data/echo_drv.c: Conform to updated driver API
Remove support for old drivers without ERL_DRV_EXTENDED_MARKER
built-in drivers: Add ERL_DRV_EXTENDED_MARKER and version numbers
Bump driver version to 2.0
erl_driver.h: Enlarge type on return value from call
erl_driver.h: Enlarge types on driver callbacks output, control and call
erl_driver.h: Enlarge types in driver output functions
...
Conflicts:
erts/emulator/test/driver_SUITE_data/monitor_drv.c
erts/emulator/test/driver_SUITE_data/timer_drv.c
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* ctime were never defined for invalid file handles
* fix epoch <-> fileinfo conversions
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Conflicts:
erts/emulator/drivers/win32/win_efile.c
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Almost all uses of the 'long' datatype is removed from VM and tests
Emulator test now runs w/o drivers crashing
Nasty abs bug fixed in VM as well as type errors in allocator debug functions
Still one allocator test that fails, domain knowledge is needed to fix that.
Fix type inconsistency in beam_load causing crashes
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Still does not run, just compiles.
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When setting file_info it will now correctly set access and
modified time. Previously these entities were swapped.
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