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Update the description for pmap_remove_pages() to match the modern

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times [1].  Assert that the pmap passed to pmap_remove_pages() is only
active on current CPU.

Submitted by:	alc [1]
Reviewed by:	alc
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
This commit is contained in:
Konstantin Belousov 2014-01-02 18:50:52 +00:00
parent c0be75a58a
commit 27fd75d2c8
1 changed files with 31 additions and 9 deletions
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40
sys/amd64/amd64/pmap.c
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@ -5123,12 +5123,20 @@ pmap_page_is_mapped(vm_page_t m)
}
/*
* Remove all pages from specified address space
* this aids process exit speeds. Also, this code
* is special cased for current process only, but
* can have the more generic (and slightly slower)
* mode enabled. This is much faster than pmap_remove
* in the case of running down an entire address space.
* Destroy all managed, non-wired mappings in the given user-space
* pmap. This pmap cannot be active on any processor besides the
* caller.
*
* This function cannot be applied to the kernel pmap. Moreover, it
* is not intended for general use. It is only to be used during
* process termination. Consequently, it can be implemented in ways
* that make it faster than pmap_remove(). First, it can more quickly
* destroy mappings by iterating over the pmap's collection of PV
* entries, rather than searching the page table. Second, it doesn't
* have to test and clear the page table entries atomically, because
* no processor is currently accessing the user address space. In
* particular, a page table entry's dirty bit won't change state once
* this function starts.
*/
void
pmap_remove_pages(pmap_t pmap)
@ -5148,10 +5156,24 @@ pmap_remove_pages(pmap_t pmap)
boolean_t superpage;
vm_paddr_t pa;
if (pmap != PCPU_GET(curpmap)) {
printf("warning: pmap_remove_pages called with non-current pmap\n");
return;
/*
* Assert that the given pmap is only active on the current
* CPU. Unfortunately, we cannot block another CPU from
* activating the pmap while this function is executing.
*/
KASSERT(pmap == PCPU_GET(curpmap), ("non-current pmap %p", pmap));
#ifdef INVARIANTS
{
cpuset_t other_cpus;
other_cpus = all_cpus;
critical_enter();
CPU_CLR(PCPU_GET(cpuid), &other_cpus);
CPU_AND(&other_cpus, &pmap->pm_active);
critical_exit();
KASSERT(CPU_EMPTY(&other_cpus), ("pmap active %p", pmap));
}
#endif
lock = NULL;
PG_M = pmap_modified_bit(pmap);