Re: [RFC PATCH v3 12/24] x86/mm: Modify ptep_set_wrprotect and pmdp_set_wrprotect for _PAGE_DIRTY_SW
From: Dave Hansen <dave.hansen@linux.intel.com>
Date: 2018-08-31 14:49:55
Also in:
linux-api, linux-arch, linux-doc, lkml
On 08/31/2018 07:33 AM, Yu-cheng Yu wrote:
Please use the form:
pte_t new_pte, pte = READ_ONCE(*ptep);
do {
new_pte = /* ... */;
} while (!try_cmpxchg(ptep, &pte, new_pte);It's probably also worth doing some testing to see if you can detect the cost of the cmpxchg. It's definitely more than the old code. A loop that does mprotect(PROT_READ) followed by mprotect(PROT_READ|PROT_WRITE) should do it.