Messages in this thread Patches in this message | | | Date | Fri, 8 Jan 1999 11:45:51 +0100 (CET) | From | Andrea Arcangeli <> | Subject | Re: arca-vm-8 [Re: [patch] arca-vm-6, killed kswapd [Re: [patch] new-vm , improvement , [Re: 2.2.0 Bug summary]]] |
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On Thu, 7 Jan 1999, Linus Torvalds wrote:
> Ok, here it is.. Stable.
Yesterday after your email I tried and I been able to reproduce the deadlock here too. It's trivial, simply alloc a shared mapping of 160Mbyte and start dirtifying it and msync it in loop. So I applyed your patch and the machine still deadlocked after some second. I thought "argg update_shared_mappings is faulting noooooo"!! So I removed updated_shared_mappings() and I tried again and it still deadlocked... I thought "oh, cool, I still have something to fix ;)".
So I developed this debugging code (that I post here because I guess it could be useful also to many others) to know which was the still pending bug:
Index: sched.c =================================================================== RCS file: /var/cvs/linux/kernel/sched.c,v retrieving revision 1.1.1.1.2.37 diff -u -r1.1.1.1.2.37 sched.c --- sched.c 1999/01/07 11:57:23 1.1.1.1.2.37 +++ sched.c 1999/01/08 10:41:53 @@ -22,6 +22,10 @@ * current-task */ +/* + * Debug down() code. Copyright (C) 1999 Andrea Arcangeli + */ + #include <linux/mm.h> #include <linux/kernel_stat.h> #include <linux/fdreg.h> @@ -893,12 +897,27 @@ tsk->state = TASK_RUNNING; \ remove_wait_queue(&sem->wait, &wait); +void generate_oops (struct semaphore *sem) +{ + sema_init(sem, 9876); + wake_up(&sem->wait); +} + void __down(struct semaphore * sem) { DOWN_VAR + struct timer_list timer; + init_timer (&timer); + timer.expires = jiffies + HZ*20; + timer.data = (unsigned long) sem; + timer.function = (void (*)(unsigned long)) generate_oops; + add_timer(&timer); DOWN_HEAD(TASK_UNINTERRUPTIBLE) schedule(); + if (atomic_read(&sem->count) == 9876) + *(int *) 0 = 0; DOWN_TAIL(TASK_UNINTERRUPTIBLE) + del_timer(&timer); } int __down_interruptible(struct semaphore * sem)
Then recompiled, rebooted, return to run the deadlocking proggy, deadlocked again after some seconds and after 20 second I had a nice Oops on the screen. SysRQ-K helped me to restore some functionality in another console. Then I run dmesg | ksymoops.... and I had this: Using `/usr/src/linux/System.map' to map addresses to symbols.
>>EIP: c0111646 <__down+b2/160> Trace: c0111574 <generate_oops> Trace: c0189f58 <__down_failed+8/10> Trace: c010ef1a <do_page_fault+56/340> Trace: c0108c0d <error_code+2d/40> Trace: c0111646 <__down+b2/160> Trace: c0111574 <generate_oops> Trace: c0189f58 <__down_failed+8/10> Trace: c011dc59 <filemap_write_page+9d/138> Trace: c011dd59 <filemap_swapout+65/7c> Trace: c0121864 <try_to_swap_out+118/1c4> Trace: c0121a18 <swap_out_vma+108/164> Trace: c0121ad4 <swap_out_process+60/88> Trace: c0121bdb <swap_out+df/fc> Trace: c011cbb7 <shrink_mmap+11b/138> Trace: c0121d1a <free_user_and_cache+1e/34> Trace: c0121d76 <try_to_free_pages+46/a4> Trace: c0122615 <__get_free_pages+d5/220> Trace: c0126af2 <get_hash_table+52/64> Trace: c0127bcf <grow_buffers+3b/ec> Trace: c0126ca8 <refill_freelist+c/34> Trace: c0126f3a <getblk+202/228> Trace: c013af6c <ext2_alloc_block+68/13c> Trace: c013b5c4 <block_getblk+15c/2b0> Trace: c013b887 <ext2_getblk+16f/20c> Trace: c0139d2b <ext2_file_write+40b/554> Trace: c011dcc0 <filemap_write_page+104/138> Trace: c011e0fe <filemap_sync+256/30c> Trace: c011e297 <msync_interval+2f/7c> Trace: c011e3d2 <sys_msync+ee/14c> Trace: c0108ad4 <system_call+34/40> Code: c0111646 <__down+b2/160> Code: c0111646 <__down+b2/160> c7 05 00 00 00 movl $0x0,0x0 Code: c011164b <__down+b7/160> 00 00 00 00 00 Code: c0111656 <__down+c2/160> 8b 75 d8 movl 0xffffffd8(%ebp),%esi Code: c0111659 <__down+c5/160> c7 06 02 00 00 movl $0x2,(%esi) Code: c011165f <__down+cb/160> 31 00 xorl %eax,(%eax) Code: c0111667 <__down+d3/160> 90 nop Code: c0111668 <__down+d4/160> 90 nop Code: c0111669 <__down+d5/160> 90 nop So I looked at buffer.c ;)
Index: buffer.c =================================================================== RCS file: /var/cvs/linux/fs/buffer.c,v retrieving revision 1.1.1.1.2.8 diff -u -r1.1.1.1.2.8 buffer.c --- buffer.c 1999/01/07 11:57:21 1.1.1.1.2.8 +++ linux/fs/buffer.c 1999/01/08 10:27:09 @@ -689,7 +689,7 @@ */ static void refill_freelist(int size) { - if (!grow_buffers(GFP_KERNEL, size)) { + if (!grow_buffers(GFP_BUFFER, size)) { wakeup_bdflush(1); current->policy |= SCHED_YIELD; schedule();
and now is really stable ;))
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