[Devel] Re: [RFC cr-pipe-v13][PATCH 2/3] Checkpoint open pipes

[Dave Hansen]

On Thu, 2009-02-05 at 20:26 -0600, Nathan Lynch wrote:
> On Thu, 05 Feb 2009 10:45:55 +0100
> Cedric Le Goater <clg at fr.ibm.com> wrote:
> > > +/* cr_write_pipebuf - dump contents of a pipe/fifo (assume i_mutex taken) */
> > > +static int cr_write_pipebuf(struct cr_ctx *ctx, struct pipe_inode_info *pipe)
> > > +{
> > > +	struct cr_hdr h;
> > > +	void *kbuf, *addr;
> > > +	int i, ret = 0;
> > > +
> > > +	kbuf = (void *) __get_free_page(GFP_KERNEL);
> > 
> > this can sleep and inode->i_mutex is locked.
> 
> Generally, it is okay to perform operations that may sleep while
> holding a mutex (not so with spinlocks, though).  Unless the page
> allocator could try to acquire the same inode->i_mutex, this code
> should be fine, no?

Sleeping inside mutexes is OK.  In general, they're drop-in compatible
with semaphore behavior.

-- Dave

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