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Code Issues Releases Activity

Document three synchronization issues in vm_fault().

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This commit is contained in:
Alan Cox 2002-04-29 05:23:01 +00:00
parent b2d9070d05
commit 532eadef77
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=95701
1 changed files with 8 additions and 0 deletions
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8
sys/vm/vm_fault.c
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@ -278,6 +278,8 @@ RetryFault:;
* Bump the paging-in-progress count to prevent size changes (e.g.
* truncation operations) during I/O. This must be done after
* obtaining the vnode lock in order to avoid possible deadlocks.
*
* XXX vnode_pager_lock() can block without releasing the map lock.
*/
vm_object_reference(fs.first_object);
fs.vp = vnode_pager_lock(fs.first_object);
@ -479,6 +481,9 @@ RetryFault:;
* vm_page_t passed to the routine.
*
* fs.m plus the additional pages are PG_BUSY'd.
*
* XXX vm_fault_additional_pages() can block
* without releasing the map lock.
*/
faultcount = vm_fault_additional_pages(
fs.m, behind, ahead, marray, &reqpage);
@ -486,6 +491,9 @@ RetryFault:;
/*
* update lastr imperfectly (we do not know how much
* getpages will actually read), but good enough.
*
* XXX The following assignment modifies the map
* without holding a write lock on it.
*/
fs.entry->lastr = fs.pindex + faultcount - behind;