80bf6ceaf9
When we get into activate_mm(), lockdep complains that we're doing
something strange:
WARNING: possible circular locking dependency detected
5.1.0-10252-gb00152307319-dirty #121 Not tainted
------------------------------------------------------
inside.sh/366 is trying to acquire lock:
(____ptrval____) (&(&p->alloc_lock)->rlock){+.+.}, at: flush_old_exec+0x703/0x8d7
but task is already holding lock:
(____ptrval____) (&mm->mmap_sem){++++}, at: flush_old_exec+0x6c5/0x8d7
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (&mm->mmap_sem){++++}:
[...]
__lock_acquire+0x12ab/0x139f
lock_acquire+0x155/0x18e
down_write+0x3f/0x98
flush_old_exec+0x748/0x8d7
load_elf_binary+0x2ca/0xddb
[...]
-> #0 (&(&p->alloc_lock)->rlock){+.+.}:
[...]
__lock_acquire+0x12ab/0x139f
lock_acquire+0x155/0x18e
_raw_spin_lock+0x30/0x83
flush_old_exec+0x703/0x8d7
load_elf_binary+0x2ca/0xddb
[...]
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&mm->mmap_sem);
lock(&(&p->alloc_lock)->rlock);
lock(&mm->mmap_sem);
lock(&(&p->alloc_lock)->rlock);
*** DEADLOCK ***
2 locks held by inside.sh/366:
#0: (____ptrval____) (&sig->cred_guard_mutex){+.+.}, at: __do_execve_file+0x12d/0x869
#1: (____ptrval____) (&mm->mmap_sem){++++}, at: flush_old_exec+0x6c5/0x8d7
stack backtrace:
CPU: 0 PID: 366 Comm: inside.sh Not tainted 5.1.0-10252-gb00152307319-dirty #121
Stack:
[...]
Call Trace:
[<600420de>] show_stack+0x13b/0x155
[<6048906b>] dump_stack+0x2a/0x2c
[<6009ae64>] print_circular_bug+0x332/0x343
[<6009c5c6>] check_prev_add+0x669/0xdad
[<600a06b4>] __lock_acquire+0x12ab/0x139f
[<6009f3d0>] lock_acquire+0x155/0x18e
[<604a07e0>] _raw_spin_lock+0x30/0x83
[<60151e6a>] flush_old_exec+0x703/0x8d7
[<601a8eb8>] load_elf_binary+0x2ca/0xddb
[...]
I think it's because in exec_mmap() we have
down_read(&old_mm->mmap_sem);
...
task_lock(tsk);
...
activate_mm(active_mm, mm);
(which does down_write(&mm->mmap_sem))
I'm not really sure why lockdep throws in the whole knowledge
about the task lock, but it seems that old_mm and mm shouldn't
ever be the same (and it doesn't deadlock) so tell lockdep that
they're different.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
83 lines
1.8 KiB
C
83 lines
1.8 KiB
C
/*
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* Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
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* Licensed under the GPL
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*/
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#ifndef __UM_MMU_CONTEXT_H
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#define __UM_MMU_CONTEXT_H
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#include <linux/sched.h>
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#include <linux/mm_types.h>
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#include <asm/mmu.h>
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extern void uml_setup_stubs(struct mm_struct *mm);
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/*
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* Needed since we do not use the asm-generic/mm_hooks.h:
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*/
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static inline int arch_dup_mmap(struct mm_struct *oldmm, struct mm_struct *mm)
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{
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uml_setup_stubs(mm);
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return 0;
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}
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extern void arch_exit_mmap(struct mm_struct *mm);
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static inline void arch_unmap(struct mm_struct *mm,
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unsigned long start, unsigned long end)
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{
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}
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static inline void arch_bprm_mm_init(struct mm_struct *mm,
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struct vm_area_struct *vma)
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{
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}
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static inline bool arch_vma_access_permitted(struct vm_area_struct *vma,
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bool write, bool execute, bool foreign)
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{
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/* by default, allow everything */
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return true;
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}
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/*
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* end asm-generic/mm_hooks.h functions
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*/
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#define deactivate_mm(tsk,mm) do { } while (0)
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extern void force_flush_all(void);
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static inline void activate_mm(struct mm_struct *old, struct mm_struct *new)
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{
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/*
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* This is called by fs/exec.c and sys_unshare()
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* when the new ->mm is used for the first time.
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*/
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__switch_mm(&new->context.id);
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down_write_nested(&new->mmap_sem, 1);
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uml_setup_stubs(new);
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up_write(&new->mmap_sem);
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}
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static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
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struct task_struct *tsk)
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{
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unsigned cpu = smp_processor_id();
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if(prev != next){
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cpumask_clear_cpu(cpu, mm_cpumask(prev));
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cpumask_set_cpu(cpu, mm_cpumask(next));
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if(next != &init_mm)
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__switch_mm(&next->context.id);
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}
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}
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static inline void enter_lazy_tlb(struct mm_struct *mm,
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struct task_struct *tsk)
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{
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}
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extern int init_new_context(struct task_struct *task, struct mm_struct *mm);
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extern void destroy_context(struct mm_struct *mm);
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#endif
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