Re: BUG-lockdep and freeze (was: Arrr! Linux 2.6.18)

From: Eric Rannaud
Date: Sat Sep 30 2006 - 17:43:42 EST

On 9/30/06, Andi Kleen <ak@xxxxxxx> wrote:
Index: linux/arch/i386/kernel/process.c
===================================================================
--- linux.orig/arch/i386/kernel/process.c
+++ linux/arch/i386/kernel/process.c
@@ -328,6 +328,7 @@ extern void kernel_thread_helper(void);
int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
{
struct pt_regs regs;
+ int err;

memset(&regs, 0, sizeof(regs));

@@ -342,7 +343,9 @@ int kernel_thread(int (*fn)(void *), voi
regs.eflags = X86_EFLAGS_IF | X86_EFLAGS_SF | X86_EFLAGS_PF | 0x2;

/* Ok, create the new process.. */
- return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
+ err = do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
+ if (err == 0) /* terminate kernel stack */
+ task_pt_regs(current)->eip = 0;
}
EXPORT_SYMBOL(kernel_thread);

Index: linux/arch/x86_64/kernel/entry.S
===================================================================
--- linux.orig/arch/x86_64/kernel/entry.S
+++ linux/arch/x86_64/kernel/entry.S
@@ -978,6 +978,11 @@ ENTRY(kernel_thread)
call do_fork
movq %rax,RAX(%rsp)
xorl %edi,%edi
+ test %rax,%rax
+ jnz 1f
+ /* terminate stack in child */
+ movq %rdi,RIP(%rsp)
+1:

/*
* It isn't worth to check for reschedule here,



For the sake of it, I tried your patch (more exactly the version at
the end of that email, againt v2.6.18). It doesn't freeze and prints
the following stack trace:

----
[ 174.630434] BUG: warning at
kernel/lockdep.c:565/print_infinite_recursion_bug()
[ 174.630506]
[ 174.630507] Call Trace:
[ 174.630703] [<ffffffff8020b23d>] show_trace+0xad/0x3b0
[ 174.630760] [<ffffffff8020b785>] dump_stack+0x15/0x20
[ 174.630819] [<ffffffff8024ba7d>] print_infinite_recursion_bug+0x3d/0x50
[ 174.630938] [<ffffffff8024bb8f>] find_usage_backwards+0x2f/0xd0
[ 174.631051] [<ffffffff8024bbf3>] find_usage_backwards+0x93/0xd0
[ 174.631163] [<ffffffff8024bbf3>] find_usage_backwards+0x93/0xd0
[ 174.631277] [<ffffffff8024bbf3>] find_usage_backwards+0x93/0xd0
[ 174.631403] [<ffffffff8024bbf3>] find_usage_backwards+0x93/0xd0
[ 174.631530] [<ffffffff8024bbf3>] find_usage_backwards+0x93/0xd0
[ 174.631655] [<ffffffff8024bbf3>] find_usage_backwards+0x93/0xd0
[ 174.631786] [<ffffffff8024bbf3>] find_usage_backwards+0x93/0xd0
[ 174.631912] [<ffffffff8024bbf3>] find_usage_backwards+0x93/0xd0
[ 174.632039] [<ffffffff8024bbf3>] find_usage_backwards+0x93/0xd0
[ 174.632166] [<ffffffff8024bbf3>] find_usage_backwards+0x93/0xd0
[ 174.632293] [<ffffffff8024bbf3>] find_usage_backwards+0x93/0xd0
[ 174.632419] [<ffffffff8024bbf3>] find_usage_backwards+0x93/0xd0
[ 174.632546] [<ffffffff8024bbf3>] find_usage_backwards+0x93/0xd0
[ 174.632672] [<ffffffff8024bbf3>] find_usage_backwards+0x93/0xd0
[ 174.632798] [<ffffffff8024bbf3>] find_usage_backwards+0x93/0xd0
[ 174.632924] [<ffffffff8024bbf3>] find_usage_backwards+0x93/0xd0
[ 174.633050] [<ffffffff8024bbf3>] find_usage_backwards+0x93/0xd0
[ 174.633176] [<ffffffff8024bbf3>] find_usage_backwards+0x93/0xd0
[ 174.633303] [<ffffffff8024bbf3>] find_usage_backwards+0x93/0xd0
[ 174.633432] [<ffffffff8024bbf3>] find_usage_backwards+0x93/0xd0
[ 174.633559] [<ffffffff8024c5a0>] check_usage+0x40/0x2b0
[ 174.633685] [<ffffffff8024de70>] __lock_acquire+0xa50/0xd20
[ 174.633811] [<ffffffff8024e4cb>] lock_acquire+0x8b/0xc0
[ 174.633941] [<ffffffff804ac5a5>] _spin_lock+0x25/0x40
[ 174.634071] [<ffffffff80227e5b>] double_rq_lock+0x2b/0x50
[ 174.634171] [<ffffffff8022b1bb>] migration_thread+0x22b/0x2e0
[ 174.634272] [<ffffffff80246dca>] kthread+0xda/0x110
[ 174.634392] [<ffffffff8020aaad>] child_rip+0xa/0x11
----

er.


diff --git a/arch/i386/kernel/process.c b/arch/i386/kernel/process.c
index 8657c73..5a7ef45 100644
--- a/arch/i386/kernel/process.c
+++ b/arch/i386/kernel/process.c
@@ -336,6 +336,7 @@ __asm__(".section .text\n"
int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
{
struct pt_regs regs;
+ int err;

memset(&regs, 0, sizeof(regs));

@@ -350,7 +351,10 @@ int kernel_thread(int (*fn)(void *), voi
regs.eflags = X86_EFLAGS_IF | X86_EFLAGS_SF | X86_EFLAGS_PF | 0x2;

/* Ok, create the new process.. */
- return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs, 0,
NULL, NULL);
+ err = do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs, 0,
NULL, NULL);
+ if (err == 0) /* terminate kernel stack */
+ task_pt_regs(current)->eip = 0;
+ return err;
}
EXPORT_SYMBOL(kernel_thread);

diff --git a/arch/x86_64/kernel/entry.S b/arch/x86_64/kernel/entry.S
index aa8d893..5dce978 100644
--- a/arch/x86_64/kernel/entry.S
+++ b/arch/x86_64/kernel/entry.S
@@ -958,6 +958,11 @@ ENTRY(kernel_thread)
call do_fork
movq %rax,RAX(%rsp)
xorl %edi,%edi
+ test %rax,%rax
+ jnz 1f
+ /* terminate stack in child */
+ movq %rdi,RIP(%rsp)
+1:

/*
* It isn't worth to check for reschedule here,
-
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