On 09/15/2016 06:18 PM, Elliott, Robert (Persistent Memory) wrote:
> 
> 
>> -----Original Message-----
>> From: Linux-nvdimm [mailto:linux-nvdimm-boun...@lists.01.org] On
>> Behalf Of Dave Jiang
>> Sent: Thursday, September 15, 2016 5:28 PM
>> To: vishal.l.ve...@intel.com
>> Cc: linux-nvdimm@lists.01.org
>> Subject: [PATCH] ndctl: move test/dax-errors buffer to global to
>> avoid gcc optimization
>>
>> Some gcc toolchain are optimizing out the memcpy and this causes dax-
>> errors
>> to not trigger the SIG_BUS when doing memcpy on an mmap'd buffer. By
>> moving
>> the buffer to a global variable this bypasses the optimization and
>> allow
>> the test to work as intended.
>>
>> Signed-off-by: Dave Jiang <dave.ji...@intel.com>
>> ---
>>  test/dax-errors.c |    4 +++-
>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/test/dax-errors.c b/test/dax-errors.c
>> index 11d0031..9ea5c91 100644
>> --- a/test/dax-errors.c
>> +++ b/test/dax-errors.c
>> @@ -17,6 +17,8 @@
>>
>>  static sigjmp_buf sj_env;
>>  static int sig_count;
>> +/* buf is global in order to avoid gcc memcpy optimization */
>> +static void *buf;
>>
>>  static void sigbus_hdl(int sig, siginfo_t *siginfo, void *ptr)
>>  {
>> @@ -27,7 +29,7 @@ static void sigbus_hdl(int sig, siginfo_t *siginfo,
>> void *ptr)
>>
>>  static int test_dax_read_err(int fd)
>>  {
>> -void *base, *buf;
>> +void *base;
>>  int rc = 0;
>>
>>  if (fd < 0) {
>>
> 
> I've run into that kind of problem before, and found that
> marking *buf as volatile (and leaving it inside the function)
> tends to be honored better by aggressive optimizing compilers
> and linkers.

I'll make the change.

> 
> ---
> Robert Elliott, HPE Persistent Memory
> 
> 
> 
_______________________________________________
Linux-nvdimm mailing list
Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm

Reply via email to