Messages in this thread |  | | | Date | Fri, 3 Jul 2009 12:16:06 +0200 | | From | Oleg Nesterov <> | | Subject | Re: [PATCH 3/3] exec: Allow do_coredump to wait for user space pipe readers to complete (v7) |
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On 07/02, Neil Horman wrote: > > +static void wait_for_dump_helpers(struct file *file) > +{ > + struct pipe_inode_info *pipe; > + > + pipe = file->f_path.dentry->d_inode->i_pipe; > + > + pipe_lock(pipe); > + pipe->readers++; > + pipe->writers--; > + > + while ((pipe->readers > 1) && (!fatal_signal_pending(current))) { > + wake_up_interruptible_sync(&pipe->wait); > + kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); > + pipe_wait(pipe); > + }
The kernel can hang on UP machine.
Suppose that rt task starts the coredump and then recieves a non-fatal signal before core_pattern app closes stdin.
In that case this "while()" above becomes a busy-wait loop which never stops. Neil, please use signal_pending() as I said. Yes, this means wait_for_ will abort if we recieve a non-fatal signal. But as I said we have other problems with signals here, when we fix them wait_for_dump_helpers() will be fixed automatically.
Oleg.
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