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

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On 9/30/06, Andi Kleen <[email protected]> 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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