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Commit 93f68f1e authored by Nathan Fontenot's avatar Nathan Fontenot Committed by Benjamin Herrenschmidt
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powerpc/pseries: Correct rtas_data_buf locking in dlpar code 



The dlpar code can cause a deadlock to occur when making the RTAS
configure-connector call.  This occurs because we make kmalloc calls,
which can block, while parsing the rtas_data_buf and holding the
rtas_data_buf_lock.  This an cause issues if someone else attempts
to grab the rtas_data_bug_lock.

This patch alleviates this issue by copying the contents of the rtas_data_buf
to a local buffer before parsing.  This allows us to only hold the
rtas_data_buf_lock around the RTAS configure-connector calls.

Signed-off-by: default avatarNathan Fontenot <nfont@austin.ibm.com>
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent a28dec2f

arch/powerpc/platforms/pseries/dlpar.c

+29 −13
Original line number Diff line number Diff line
@@ -129,20 +129,35 @@ struct device_node *dlpar_configure_connector(u32 drc_index) 
	struct property *property;

	struct property *last_property = NULL;

	struct cc_workarea *ccwa;

	char *data_buf;

	int cc_token;

	int rc;

	int rc = -1;



	cc_token = rtas_token("ibm,configure-connector");

	if (cc_token == RTAS_UNKNOWN_SERVICE)

		return NULL;



	spin_lock(&rtas_data_buf_lock);

	ccwa = (struct cc_workarea *)&rtas_data_buf[0];

	data_buf = kzalloc(RTAS_DATA_BUF_SIZE, GFP_KERNEL);

	if (!data_buf)

		return NULL;



	ccwa = (struct cc_workarea *)&data_buf[0];

	ccwa->drc_index = drc_index;

	ccwa->zero = 0;



	do {

		/* Since we release the rtas_data_buf lock between configure

		 * connector calls we want to re-populate the rtas_data_buffer

		 * with the contents of the previous call.

		 */

		spin_lock(&rtas_data_buf_lock);



		memcpy(rtas_data_buf, data_buf, RTAS_DATA_BUF_SIZE);

		rc = rtas_call(cc_token, 2, 1, NULL, rtas_data_buf, NULL);

	while (rc) {

		memcpy(data_buf, rtas_data_buf, RTAS_DATA_BUF_SIZE);



		spin_unlock(&rtas_data_buf_lock);



		switch (rc) {

		case NEXT_SIBLING:

			dn = dlpar_parse_cc_node(ccwa);
@@ -197,20 +212,21 @@ struct device_node *dlpar_configure_connector(u32 drc_index) 
			       "returned from configure-connector\n", rc);

			goto cc_error;

		}



		rc = rtas_call(cc_token, 2, 1, NULL, rtas_data_buf, NULL);

	}



	spin_unlock(&rtas_data_buf_lock);

	return first_dn;

	} while (rc);



cc_error:

	kfree(data_buf);



	if (rc) {

		if (first_dn)

			dlpar_free_cc_nodes(first_dn);

	spin_unlock(&rtas_data_buf_lock);



		return NULL;

	}



	return first_dn;

}



static struct device_node *derive_parent(const char *path)

{

	struct device_node *parent;