Messages in this thread | | | Date | Wed, 1 Jul 2009 18:06:10 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 3/3] exec: Allow do_coredump to wait for user space pipe readers to complete (v5) |
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Neil, the changelog is not right,
On 07/01, Neil Horman wrote: > > We basically add ourselves as an additional > reader (to prevent cleanup of the pipe), write the dump in ->core_dump(),
This is not what we do. We do not and must not inc readers before ->core_dump(). We only do this in wait_for_dump_helpers().
> note that we add ourselves as a reader before writing the > file. this closes the race in the window between the time we write the dump and > the time we start checking for the user space process to be done with the pipe.
again, this doesn't match the patch.
> +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) { > + wake_up_interruptible_sync(&pipe->wait); > + kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); > + pipe_wait(pipe); > + } > + > + /* > + * This reclaims the additional readers count we took in > + * do_coredump > + */
now the comment is wrong.
Can't understand why do you change readers/writers unconditianally, we shouldn't have the false wakeups since ->writers == 0, but OK.
Oleg.
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