linux-kernel - Re: [ia64] BUG: sleeping in atomic

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Message-ID: <20071219164204.GA18161@fattire.cabal.ca>
Date:	Wed, 19 Dec 2007 11:42:04 -0500
From:	Kyle McMartin <kyle@...artin.ca>
To:	David Chinner <dgc@....com>
Cc:	lkml <linux-kernel@...r.kernel.org>, tony.luck@...el.com,
	linux-ia64@...r.kernel.org
Subject: Re: [ia64] BUG: sleeping in atomic

On Wed, Dec 19, 2007 at 04:54:30PM +1100, David Chinner wrote:
> [ 5667.086055] BUG: sleeping function called from invalid context at kernel/fork.c:401
> 

The problem is that mmput is called under the read_lock by
find_thread_for_addr... The comment above seems to indicate that gdb
needs to be able to access any child tasks register backing store
memory... This seems pretty broken.

cheers, Kyle

---

Who knows, maybe gdb is saner now?

diff --git a/arch/ia64/kernel/ptrace.c b/arch/ia64/kernel/ptrace.c
index 2e96f17..b609704 100644
--- a/arch/ia64/kernel/ptrace.c
+++ b/arch/ia64/kernel/ptrace.c
@@ -1418,7 +1418,7 @@ asmlinkage long
 sys_ptrace (long request, pid_t pid, unsigned long addr, unsigned long data)
 {
 	struct pt_regs *pt;
-	unsigned long urbs_end, peek_or_poke;
+	unsigned long urbs_end;
 	struct task_struct *child;
 	struct switch_stack *sw;
 	long ret;
@@ -1430,23 +1430,12 @@ sys_ptrace (long request, pid_t pid, unsigned long addr, unsigned long data)
 		goto out;
 	}
 
-	peek_or_poke = (request == PTRACE_PEEKTEXT
-			|| request == PTRACE_PEEKDATA
-			|| request == PTRACE_POKETEXT
-			|| request == PTRACE_POKEDATA);
-	ret = -ESRCH;
-	read_lock(&tasklist_lock);
-	{
-		child = find_task_by_pid(pid);
-		if (child) {
-			if (peek_or_poke)
-				child = find_thread_for_addr(child, addr);
-			get_task_struct(child);
-		}
-	}
-	read_unlock(&tasklist_lock);
-	if (!child)
+	child = ptrace_get_task_struct(pid);
+	if (IS_ERR(child)) {
+		ret = PTR_ERR(child);
 		goto out;
+	}
+
 	ret = -EPERM;
 	if (pid == 1)		/* no messing around with init! */
 		goto out_tsk;
--
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