Messages in this thread Patch in this message | | | Date | Thu, 26 Jan 2006 01:02:00 +0100 | From | Ingo Molnar <> | Subject | [patch, lock validator] fix proc_inum_lock related deadlock |
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there's another VFS lock that just popped up, hopefully the last one. Fix below. (All this is still related to proc_subdir_lock, and the original BKL bug it fixed.)
Ingo
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&proc_inum_lock also nests within proc_subdir_lock, and &proc_inum_lock is used in a softirq-unsafe manner. The lock validator noticed the following scenario:
===================================== [ BUG: lock inversion bug detected! ] ------------------------------------- ifup-eth/2308 just changed the state of lock {proc_subdir_lock} at: [<c0197083>] remove_proc_entry+0x33/0x1f0 but this lock took lock {proc_inum_lock} in the past, acquired at: [<c0196fee>] free_proc_entry+0x2e/0x90 and interrupts could create an inverse lock dependency between them, which could lead to deadlocks!
other info that might help in debugging this: locks held by ifup-eth/2308: [<c010432d>] show_trace+0xd/0x10 [<c0104347>] dump_stack+0x17/0x20 [<c0137a41>] check_no_lock_2_mask+0x131/0x180 [<c013852b>] mark_lock+0xfb/0x2a0 [<c0138b63>] debug_lock_chain+0x493/0xdc0 [<c01394cd>] debug_lock_chain_spin+0x3d/0x60 [<c026594d>] _raw_spin_lock+0x2d/0x90 [<c04d91a2>] _spin_lock_bh+0x12/0x20 [<c0197083>] remove_proc_entry+0x33/0x1f0 [<c01429e9>] unregister_handler_proc+0x19/0x20 [<c01421ab>] free_irq+0x7b/0xe0 [<c02f25b2>] floppy_release_irq_and_dma+0x1b2/0x210 [<c02f0aa7>] set_dor+0xc7/0x1b0 [<c02f3b21>] motor_off_callback+0x21/0x30 [<c01274d5>] run_timer_softirq+0xf5/0x1f0 [<c0122e27>] __do_softirq+0x97/0x130 [<c0105519>] do_softirq+0x69/0x100 =======================
the fix is to take proc_inum_lock in a softirq-safe manner.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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fs/proc/generic.c | 8 ++++---- 1 files changed, 4 insertions(+), 4 deletions(-)
Index: linux/fs/proc/generic.c =================================================================== --- linux.orig/fs/proc/generic.c +++ linux/fs/proc/generic.c @@ -329,9 +329,9 @@ retry: if (idr_pre_get(&proc_inum_idr, GFP_KERNEL) == 0) return 0; - spin_lock(&proc_inum_lock); + spin_lock_bh(&proc_inum_lock); error = idr_get_new(&proc_inum_idr, NULL, &i); - spin_unlock(&proc_inum_lock); + spin_unlock_bh(&proc_inum_lock); if (error == -EAGAIN) goto retry; else if (error) @@ -350,9 +350,9 @@ static void release_inode_number(unsigne { int id = (inum - PROC_DYNAMIC_FIRST) | ~MAX_ID_MASK; - spin_lock(&proc_inum_lock); + spin_lock_bh(&proc_inum_lock); idr_remove(&proc_inum_idr, id); - spin_unlock(&proc_inum_lock); + spin_unlock_bh(&proc_inum_lock); } static void *proc_follow_link(struct dentry *dentry, struct nameidata *nd) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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