xtensa: Use default malloc alignment of 8 #5
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The current malloc implementation has a bug in which the first malloc call may fail if MALLOC_ALIGNMENT is 16 and the requested block size is such that malloc invokes sbrk with the heap expansion size that causes the resulting heap address to fall on a page boundary. sys/config.h was defining the minimum MALLOC_ALIGNMENT for the Xtensa architecture as 16, and this caused the first malloc call to fail on the Xtensa platforms in some rare cases that satisfy the conditions described above (see zephyrproject-rtos/zephyr#38258). Since the Xtensa architecture in itself does not require the malloc alignment of 16, remove MALLOC_ALIGNMENT definition and use the default alignment of 8 for all Xtensa platforms. Signed-off-by: Stephanos Ioannidis <root@stephanos.io>
| @@ -195,7 +195,6 @@ | |||
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| #ifdef __XTENSA__ | |||
| #include <xtensa/config/core-isa.h> | |||
| #define MALLOC_ALIGNMENT ((XCHAL_DATA_WIDTH) < 16 ? 16 : (XCHAL_DATA_WIDTH)) | |||
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Hmm, looks like imx sets XCHAL_DATA_WIDTH to 16. So wonder if this should be
#define MALLOC_ALIGNMENT XCHAL_DATA_WIDTH
Guessing that will still cause issues on xtensa for i.mx?
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Guessing that will still cause issues on xtensa for i.mx?
@galak Yes, this issue will persist as long as MALLOC_ALIGNMENT is 16 (and maybe others except 8 too) since we are not fixing the root cause here.
While it would be nice to fix the malloc itself, I do not have bandwidth to debug and fix it at the moment.
As for the i.MX with XCHAL_DATA_WIDTH of 16, I do not think there will be any issues using the MALLOC_ALIGNMENT of 8 other than some minor performance penalties for the conventional un-optimised code.
The current malloc implementation has a bug in which the first malloc
call may fail if MALLOC_ALIGNMENT is 16 and the requested block size is
such that malloc invokes sbrk with the heap expansion size that causes
the resulting heap address to fall on a page boundary.
sys/config.h was defining the minimum MALLOC_ALIGNMENT for the Xtensa
architecture as 16, and this caused the first malloc call to fail on
the Xtensa platforms in some rare cases that satisfy the conditions
described above (see zephyrproject-rtos/zephyr#38258).
Since the Xtensa architecture in itself does not require the malloc
alignment of 16, remove MALLOC_ALIGNMENT definition and use the default
alignment of 8 for all Xtensa platforms.
Signed-off-by: Stephanos Ioannidis root@stephanos.io