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x86: finish user fault error path with fatal signal
The x86 fault handler bails in the middle of error handling when the task has a fatal signal pending. For a subsequent patch this is a problem in OOM situations because it relies on pagefault_out_of_memory() being called even when the task has been killed, to perform proper per-task OOM state unwinding. Shortcutting the fault like this is a rather minor optimization that saves a few instructions in rare cases. Just remove it for user-triggered faults. Use the opportunity to split the fault retry handling from actual fault errors and add locking documentation that reads suprisingly similar to ARM's. Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Reviewed-by: Michal Hocko <mhocko@suse.cz> Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: David Rientjes <rientjes@google.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: azurIt <azurit@pobox.sk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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parent
759496ba64
commit
3a13c4d761
1 changed files with 17 additions and 18 deletions
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@ -842,23 +842,15 @@ do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
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force_sig_info_fault(SIGBUS, code, address, tsk, fault);
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}
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static noinline int
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static noinline void
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mm_fault_error(struct pt_regs *regs, unsigned long error_code,
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unsigned long address, unsigned int fault)
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{
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/*
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* Pagefault was interrupted by SIGKILL. We have no reason to
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* continue pagefault.
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*/
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if (fatal_signal_pending(current)) {
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if (!(fault & VM_FAULT_RETRY))
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up_read(¤t->mm->mmap_sem);
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if (!(error_code & PF_USER))
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no_context(regs, error_code, address, 0, 0);
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return 1;
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if (fatal_signal_pending(current) && !(error_code & PF_USER)) {
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up_read(¤t->mm->mmap_sem);
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no_context(regs, error_code, address, 0, 0);
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return;
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}
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if (!(fault & VM_FAULT_ERROR))
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return 0;
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if (fault & VM_FAULT_OOM) {
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/* Kernel mode? Handle exceptions or die: */
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@ -866,7 +858,7 @@ mm_fault_error(struct pt_regs *regs, unsigned long error_code,
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up_read(¤t->mm->mmap_sem);
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no_context(regs, error_code, address,
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SIGSEGV, SEGV_MAPERR);
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return 1;
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return;
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}
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up_read(¤t->mm->mmap_sem);
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@ -884,7 +876,6 @@ mm_fault_error(struct pt_regs *regs, unsigned long error_code,
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else
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BUG();
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}
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return 1;
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}
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static int spurious_fault_check(unsigned long error_code, pte_t *pte)
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@ -1189,9 +1180,17 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code)
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*/
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fault = handle_mm_fault(mm, vma, address, flags);
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if (unlikely(fault & (VM_FAULT_RETRY|VM_FAULT_ERROR))) {
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if (mm_fault_error(regs, error_code, address, fault))
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return;
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/*
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* If we need to retry but a fatal signal is pending, handle the
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* signal first. We do not need to release the mmap_sem because it
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* would already be released in __lock_page_or_retry in mm/filemap.c.
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*/
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if (unlikely((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)))
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return;
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if (unlikely(fault & VM_FAULT_ERROR)) {
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mm_fault_error(regs, error_code, address, fault);
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return;
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}
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/*
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