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[PATCH] mm: flush_tlb_range outside ptlock 

There was one small but very significant change in the previous patch:
mprotect's flush_tlb_range fell outside the page_table_lock: as it is in 2.4,
but that doesn't prove it safe in 2.6.

On some architectures flush_tlb_range comes to the same as flush_tlb_mm, which
has always been called from outside page_table_lock in dup_mmap, and is so
proved safe.  Others required a deeper audit: I could find no reliance on
page_table_lock in any; but in ia64 and parisc found some code which looks a
bit as if it might want preemption disabled.  That won't do any actual harm,
so pending a decision from the maintainers, disable preemption there.

Remove comments on page_table_lock from flush_tlb_mm, flush_tlb_range and
flush_tlb_page entries in cachetlb.txt: they were rather misleading (what
generic code does is different from what usually happens), the rules are now
changing, and it's not yet clear where we'll end up (will the generic
tlb_flush_mmu happen always under lock?  never under lock?  or sometimes under
and sometimes not?).

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Hugh Dickins 2005-10-29 18:16:28 -07:00 committed by Linus Torvalds
parent 705e87c0c3
commit 663b97f7ef
3 changed files with 4 additions and 10 deletions
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9
Documentation/cachetlb.txt
View File

@ -49,9 +49,6 @@ changes occur:
page table operations such as what happens during
fork, and exec.
Platform developers note that generic code will always
invoke this interface without mm->page_table_lock held.
3) void flush_tlb_range(struct vm_area_struct *vma,
unsigned long start, unsigned long end)
@ -72,9 +69,6 @@ changes occur:
call flush_tlb_page (see below) for each entry which may be
modified.
Platform developers note that generic code will always
invoke this interface with mm->page_table_lock held.
4) void flush_tlb_page(struct vm_area_struct *vma, unsigned long addr)
This time we need to remove the PAGE_SIZE sized translation
@ -93,9 +87,6 @@ changes occur:
This is used primarily during fault processing.
Platform developers note that generic code will always
invoke this interface with mm->page_table_lock held.
5) void flush_tlb_pgtables(struct mm_struct *mm,
unsigned long start, unsigned long end)

2
arch/ia64/mm/tlb.c
View File

@ -158,10 +158,12 @@ flush_tlb_range (struct vm_area_struct *vma, unsigned long start, unsigned long
# ifdef CONFIG_SMP
platform_global_tlb_purge(mm, start, end, nbits);
# else
preempt_disable();
do {
ia64_ptcl(start, (nbits<<2));
start += (1UL << nbits);
} while (start < end);
preempt_enable();
# endif
ia64_srlz_i(); /* srlz.i implies srlz.d */

3
include/asm-parisc/tlbflush.h
View File

@ -88,7 +88,7 @@ static inline void flush_tlb_range(struct vm_area_struct *vma,
if (npages >= 512) /* 2MB of space: arbitrary, should be tuned */
flush_tlb_all();
else {
preempt_disable();
mtsp(vma->vm_mm->context,1);
purge_tlb_start();
if (split_tlb) {
@ -102,6 +102,7 @@ static inline void flush_tlb_range(struct vm_area_struct *vma,
pdtlb(start);
start += PAGE_SIZE;
}
preempt_enable();
}
purge_tlb_end();
}