[Issue 13727] std.stdio.File not thread-safe

https://issues.dlang.org/show_bug.cgi?id=13727 Vladimir Panteleev <thecybershadow@gmail.com> changed: What |Removed |Added ---------------------------------------------------------------------------- See Also| |https://issues.dlang.org/sh | |ow_bug.cgi?id=11862 --

https://issues.dlang.org/show_bug.cgi?id=13727 --- Comment #1 from Vladimir Panteleev <thecybershadow@gmail.com> --- Note that even though the above example has all threads reading from the same file, this doesn't matter, as the problem occurs even when accessing distinct files. --

https://issues.dlang.org/show_bug.cgi?id=13727 --- Comment #3 from Vladimir Panteleev <thecybershadow@gmail.com> --- (In reply to Steven Schveighoffer from comment #2) > I'm going to throw a shot in the dark out here, and say it's an issue with DMC runtime. Which means it's really a problem with DMC, not DMD or phobos. I agree. However, we might be able to work around thread safety issues in the DMC runtime using global locks. > I'll note that the DMC runtime has a limit of 64 file descriptors, including the standard handles. This shouldn't be relevant except when running the test program on systems with 64 or more processors/cores. --

https://issues.dlang.org/show_bug.cgi?id=13727 --- Comment #4 from Steven Schveighoffer <schveiguy@yahoo.com> --- (In reply to Vladimir Panteleev from comment #3) > (In reply to Steven Schveighoffer from comment #2) > > I'm going to throw a shot in the dark out here, and say it's an issue with DMC runtime. Which means it's really a problem with DMC, not DMD or phobos. > > I agree. However, we might be able to work around thread safety issues in the DMC runtime using global locks. Oh god! More locks :) I strongly believe we should fix the issue in DMC. Can we create a C++ program that will exhibit the same issue? > > > I'll note that the DMC runtime has a limit of 64 file descriptors, including the standard handles. > > This shouldn't be relevant except when running the test program on systems with 64 or more processors/cores. Oh, I didn't realize how the parallel foreach worked. --

November 14, 2014

[Issue 13727] std.stdio.File not thread-safe

Posted by Vladimir Panteleev

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Vladimir Panteleev

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https://issues.dlang.org/show_bug.cgi?id=13727

--- Comment #5 from Vladimir Panteleev <thecybershadow@gmail.com> ---
(In reply to Steven Schveighoffer from comment #4)
> Oh god! More locks :)

Assuming we don't need to lock for the actual I/O operations (read/write), I
think the impact for locking on some O(1)-ish operations shouldn't be too bad
compared to the cost of the actual I/O.

> I strongly believe we should fix the issue in DMC. Can we create a C++ program that will exhibit the same issue?

Yes:

///////////////////////////// test.c ////////////////////////////
#include <windows.h>
#include <stdio.h>

DWORD WINAPI ThreadProc(LPVOID lpParameter)
{
    for (int i=0; i<100; i++)
    {
        int res;
        FILE* f = fopen("test.c", "rb");
        if (!f) { printf("fopen failed\n"); return 1; }
        res = fclose(f);
        if (res) { printf("fclose failed\n"); return 1; }
    }
    return 0;
}

void main()
{
    for (int i=0; i<10; i++)
    {
        DWORD dwThreadId;
        CreateThread(NULL, 0, &ThreadProc, NULL, 0, &dwThreadId);
    }
}
/////////////////////////////////////////////////////////////////

--

https://issues.dlang.org/show_bug.cgi?id=13727 --- Comment #6 from Vladimir Panteleev <thecybershadow@gmail.com> --- > I strongly believe we should fix the issue in DMC. BTW, I agree in principle, but I don't know how realistic this is, considering it's closed-source and I don't know how hard or quick it is to get a patch in. --

https://issues.dlang.org/show_bug.cgi?id=13727 Steven Schveighoffer <schveiguy@yahoo.com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |bugzilla@digitalmars.com --- Comment #7 from Steven Schveighoffer <schveiguy@yahoo.com> --- (In reply to Vladimir Panteleev from comment #6) > > I strongly believe we should fix the issue in DMC. > > BTW, I agree in principle, but I don't know how realistic this is, considering it's closed-source and I don't know how hard or quick it is to get a patch in. It's on github, but private. Ask Walter for access. I fixed an issue once with pipes that was holding up std.process, so I still have access. I will warn you, though, you can't build it unless you have some obscure assembler :) At the very least, your sample code should be filed as a DMC bug, but I'm not sure where that goes. CC'ing Walter on this. --

https://issues.dlang.org/show_bug.cgi?id=13727 Vladimir Panteleev <thecybershadow@gmail.com> changed: What |Removed |Added ---------------------------------------------------------------------------- Keywords| |pull --- Comment #8 from Vladimir Panteleev <thecybershadow@gmail.com> --- https://github.com/DigitalMars/dmc/pull/2 (access required) --

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