David Chinner wrote: > On Wed, Dec 19, 2007 at 11:42:04AM -0500, Kyle McMartin wrote: > >> 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? >> Well, gdb is saner, but the bug you're talking about will be fixed in a clean way (even for insane debuggers) with Shaohua's, Roland's and my fixes to handling the RSE, because they make it possible to get rid of find_thread_for_addr(). I already sent a mail about it to linux-ia64 some time ago, and Roland suggested we might even change everything to the generic sys_ptrace(), which is the correct solution (TM), and I'm planning to do it so as soon as the RSE patches are in. Regards, Petr Tesarik >> 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; >> > > Yes, this patch fixes the problem (though I haven't tried to > use gdb yet). > > Cheers, > > Dave. > - To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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