Re: [PATCH] selftests/powerpc: Add test to check is DSCR is corrupted.

[Michael Ellerman <mpe@ellerman.id.au>]

Hi Rashmica,

Just a few nits ...

Your subject: selftests/powerpc: Add test to check is DSCR is corrupted.

Looks like it might want to be "if DSCR is" ?

On Wed, 2015-12-02 at 11:02 +1100, Rashmica Gupta wrote:

> If the transaction is aborted, the DSCR should be rolled back to the
> checkpointed value before the transaction began.
> 
> Signed-off-by: Rashmica Gupta <rashmicy@gmail.com>
> ---
> To check this yourself, undo the changes from the patch "powerpc/tm: Fix
> context switching TAR, PPR and DSCR SPRs".

Thanks for checking that actually makes it work.

That would be worth having in the commit message too, formatted like:

28e61cc466d8 ("powerpc/tm: Fix context switching TAR, PPR and DSCR SPRs")


>  tools/testing/selftests/powerpc/tm/.gitignore |  1 +
>  tools/testing/selftests/powerpc/tm/Makefile   |  2 +-
>  tools/testing/selftests/powerpc/tm/tm-dscr.c  | 91 +++++++++++++++++++++++++++
>  3 files changed, 93 insertions(+), 1 deletion(-)
>  create mode 100644 tools/testing/selftests/powerpc/tm/tm-dscr.c
> 
> diff --git a/tools/testing/selftests/powerpc/tm/.gitignore b/tools/testing/selftests/powerpc/tm/.gitignore
> index d0c7c97e9b13..76eae258feeb 100644
> --- a/tools/testing/selftests/powerpc/tm/.gitignore
> +++ b/tools/testing/selftests/powerpc/tm/.gitignore
> @@ -3,3 +3,4 @@ tm-syscall
>  tm-signal-msr-resv
>  tm-signal-stack
>  tm-fork
> +tm-dscr
> diff --git a/tools/testing/selftests/powerpc/tm/Makefile b/tools/testing/selftests/powerpc/tm/Makefile
> index f7d4727662aa..59eec240339d 100644
> --- a/tools/testing/selftests/powerpc/tm/Makefile
> +++ b/tools/testing/selftests/powerpc/tm/Makefile
> @@ -1,4 +1,4 @@
> -TEST_PROGS := tm-resched-dscr tm-syscall tm-signal-msr-resv tm-signal-stack tm-fork
> +TEST_PROGS := tm-resched-dscr tm-syscall tm-signal-msr-resv tm-signal-stack tm-fork tm-dscr

It's probably time to wrap that line.

> diff --git a/tools/testing/selftests/powerpc/tm/tm-dscr.c b/tools/testing/selftests/powerpc/tm/tm-dscr.c
> new file mode 100644
> index 000000000000..ac44e259c86d
> --- /dev/null
> +++ b/tools/testing/selftests/powerpc/tm/tm-dscr.c
> @@ -0,0 +1,91 @@
> +/*
> + * Copyright 2015, Michael Neuling, IBM Corp. 
> + * Licensed under GPLv2.
> + * Original: Michael Neuling 19/7/2013
> + * Edited: Rashmica Gupta 01/12/2015

This should probably just be:

> + * Copyright 2013-2015, Michael Neuling, Rashmica Gupta, IBM Corp.
> + *
> + * Licensed under GPLv2.

> + *
> + * Do some transactions, see if the dscr is corrupted. 
> + *

Spare blank line there.

> + */
> +
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <unistd.h>
> +#include <string.h>
> +
> +#include "tm.h"
> +#include "utils.h"
> +
> +#define SPRN_DSCR	0x3
> +
> +int	num_loops	= 10000;

Don't use tabs there please.

And num_loops can be static.

> +int test_dscr(void)

Can be static.

> +{
> +	int i;
> +
> +	SKIP_IF(!have_htm());
> +
> +	for (i = 0; i < num_loops; i++)
> +	{
> +		uint64_t result = 0;
> +		asm __volatile__(
> +			"li	7, 1;"
> +			"mtspr	%[dscr], 7;"	// dscr = 1
> +			"tbegin.;"
> +			"beq	3f ;"
> +			"li	4, 0x7000;"	// Loop lots, to use time
> +			"2: ;"		     	// Start loop
> +			"li	7, 2;"
> +			"mtspr	%[dscr], 7;"	// dscr = 2
> +			"tsuspend.;"
> +			"li	7, 3;"		
> +			"mtspr	%[dscr], 7;"	// dscr = 3
> +			"tresume.;"		
> +			"subi	4, 4, 1;"
> +			"cmpdi	4, 0;"
> +			"bne	2b;"
> +			"tend.;"
> +
> +			// Transaction sucess! DSCR should be 3.
> +			"mfspr  7, %[dscr];" 
> +			"ori	%[res], 7, 4;"	// res = 3|4 = 7
> +			"b	4f;"
> +			
> +			// Abort handler. DSCR should be rolled back to 1.
> +			"3:;" 			
> +			"mfspr  7, %[dscr];" 	

You have a bunch of trailing whitespace above which woule be nice to clean up.

> +			"ori	%[res], 7, 8;"	// res = 1|8 = 9
> +			"4:;"
> +
> +			: [res]"=r"(result)
> +			: [dscr]"i"(SPRN_DSCR)
> +			: "memory", "r0", "r4", "r7");
> +
> +		// If result is anything else other than 7 or 9, the dscr
> +		// value must have been corrupted.

Please use /* .. */ style comments for multi-line comments.

> +		if ((result != 7) && (result != 9))
> +			return 1;
> +		
> +	}

You have a spare blank line there before the }.

But you need one here after the }.

> +	return 0;
> +}
> +
> +int main(int argc, char *argv[])
> +{
> +	

Spare blank line.

> +	// A low number of iterations (eg 100) can cause a false pass.
> +	if (argc > 1) {
> +		if (strcmp(argv[1], "-h") == 0) {
> +			printf("Syntax:\n\t%s [<num loops>]\n",
> +			       argv[0]);

This would usually be:

Usage: tm-dscr [num loops]

I wouldn't bother using argv[0].

> +			return 0;
> +		} else {
> +			num_loops = atoi(argv[1]);
> +		}
> +	}
> +
> +	printf("Starting, %d loops\n", num_loops);
> +
> +	test_harness(test_dscr, "tm_dscr");

The test name should probably be the same as the binary, ie. "tm-dscr".

> +}

cheers