make raid5 checksums preempt-safe

include/asm-i386/xor.h +5 -2

@@ -543,6 +545,7 @@
 #define XMMS_SAVE				\
+	preempt_disable();			\
 	__asm__ __volatile__ ( 			\
 		"movl %%cr0,%0		;\n\t"	\
 		"clts			;\n\t"	\

@@ -564,7 +567,8 @@
 		"movl 	%0,%%cr0	;\n\t"	\
 		:				\
 		: "r" (cr0), "r" (xmm_save)	\
-		: "memory")
+		: "memory")			\
+	preempt_enable();

@@ -38,7 +38,8 @@
 #define XMMS_SAVE				\
-	asm volatile ( 			\
+	preempt_disable();			\
+	asm volatile (				\
 		"movq %%cr0,%0		;\n\t"	\
 		"clts			;\n\t"	\
 		"movups %%xmm0,(%1)	;\n\t"	\

These will suck when on if, I guess...

Anyway, will this compile at all? There seems no semicolon after the asm volatile ()

Quoted 1 line · Thunder from the hill

These will suck when on if, I guess...

hm?

Quoted 2 lines

Anyway, will this compile at all? There seems no semicolon after the asm volatile ()

Ah yes, curses. Thanks.

Also, kindly place "do { ... } while(0)" around XMMS_SAVE, if only for symmetry.

I need to close all the none std[in|out|err] open fd's.

I've been told to do it like so:

  {
    int i;
    for (i=3; i<OPEN_MAX; i++)
      close(i);
  }

This is very slow, plus I have discovered that I can have open fd's with values greater than OPEN_MAX.

I thought about getting the max fd from rlimit, but that doesn't work either. Say I have a rlimit of 1024 open fd's, and I open numbers 3 thru 1023, then I close 3 thru 1022, then I set the rlimit down to
16. rlimit then returns 16, but the largest open fd is still 1023.

So that doesn't work.

And I still have the problem that looping between 3 and whatever I pick as the top and calling close on each in turn is very slow.

So what's the "right way" to do it?

I would *love* for there to be an ioctl or some syscall that I could pass a pointer to an int and a pointer to an int array, and it would come back telling me how many open fd's I've got, and fill in the array with those fd's.

Signature · 4 lines

Mark Atwood   | Well done is better than well said.
[email protected] | 
http://www.pobox.com/~mra
-

tricky. You can use /proc/<getpid>/fd, and close all handles listed here, but this has some caveats:
it's _very_ slow if you have many open files. it's not portable.
it's not safe if you have a thread/signal handler running.

i never heard of a right way to do this.

-alex

int close_all_fd()

{
    char fdpath[PATH_MAX];
    DIR * dp;
    struct dirent * de;
    int fd;

    sprintf(fdpath, "/proc/%d/fd", getpid());
    dp = opendir(fdpath);

Quoted 17 lines · Alex Riesen

tricky. You can use /proc/<getpid>/fd, and close all handles listed here, but this has some caveats:
it's _very_ slow if you have many open files. it's not portable.
it's not safe if you have a thread/signal handler running.

i never heard of a right way to do this.

-alex

int close_all_fd()

{
    char fdpath[PATH_MAX];
    DIR * dp;
    struct dirent * de;
    int fd;

Quoted 2 lines

    sprintf(fdpath, "/proc/%d/fd", getpid());
    dp = opendir(fdpath);

This can just be:

	dp = opendir("/proc/self/fd/");

then you don't need fdpath.

You can use sigprocmask() if you're worried about signals coming in during this operation.

So what's the "right way" to do it?

I would *love* for there to be an ioctl or some syscall that I could pass a pointer to an int and a pointer to an int array, and it would come back telling me how many open fd's I've got, and fill in the array with those fd's.

Linus,

The raid5 xor checksums use MMX/SSE state and are not preempt-safe.

Attached patch disables preemption in FPU_SAVE and XMMS_SAVE and restores it in FPU_RESTORE and XMMS_RESTORE - preventing preemption while in fp mode.

Please, apply.

Robert Love