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NAND: fix race in nand_base

PATCH In review Artem Bityutskiy 1 participant 2 messages Jul 23, 2007

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Memory technology devices (MTD) NAND flash
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Artem Bityutskiy

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PATCH 1/1 NAND: fix race in nand_base

From: Artem Bityutskiy <[email protected]>
Date: Mon, 23 Jul 2007 16:06:50 +0300
Subject: [PATCH] [MTD] NAND: fix race in nand_base

When we mark block bad we have to get chip because this involves writing to the page's OOB. We hit this bug in UBI - we observed random obscure crashes when it marks block bad from the background thread and there is some parallel task which utilizes flash.

Signed-off-by Artem Bityutskiy <[email protected]>
---
 drivers/mtd/nand/nand_base.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)
drivers/mtd/nand/nand_base.c +4 -0
index 7e68203..3391b05 100644
@@ -348,6 +348,8 @@ static int nand_default_block_markbad(struct mtd_info *mtd, loff_t ofs)
 	uint8_t buf[2] = { 0, 0 };
 	int block, ret;
 
+	nand_get_device(chip, mtd, FL_READING);
+
 	/* Get block number */
 	block = (int)(ofs >> chip->bbt_erase_shift);
 	if (chip->bbt)

@@ -370,6 +372,8 @@ static int nand_default_block_markbad(struct mtd_info *mtd, loff_t ofs)
 	}
 	if (!ret)
 		mtd->ecc_stats.badblocks++;
+
+	nand_release_device(mtd);
 	return ret;
 }
Signature · 6 lines
1.5.0.6


-- 
Best regards,
Artem Bityutskiy (Битюцкий Артём)
author
#1 lore raw

drivers/mtd/nand/nand_base.c static int nand_default_block_markbad(struct mtd_info *mtd, loff_t ofs) · line 351

Quoted 9 lines · Artem Bityutskiy
drivers/mtd/nand/nand_base.c +1 -0
index 7e68203..3391b05 100644
@@ -348,6 +348,8 @@ static int nand_default_block_markbad(struct mtd_info *mtd, loff_t ofs)
 	uint8_t buf[2] = { 0, 0 };
 	int block, ret;
 
+	nand_get_device(chip, mtd, FL_READING);

Err, this should be FL_WRITING I guess.

drivers/mtd/nand/nand_base.c static int nand_default_block_markbad(struct mtd_info *mtd, loff_t ofs) · line 378

Quoted 12 lines
drivers/mtd/nand/nand_base.c +3 -0
+
 	/* Get block number */
 	block = (int)(ofs >> chip->bbt_erase_shift);
 	if (chip->bbt)

@@ -370,6 +372,8 @@ static int nand_default_block_markbad(struct mtd_info *mtd, loff_t ofs)
 	}
 	if (!ret)
 		mtd->ecc_stats.badblocks++;
+
+	nand_release_device(mtd);
 	return ret;
 }

There is still the problem with nand_update_bbt() which in turn calls mtd->read() which will deadlock. I have not found how BBT is protected. Any suggestions/pointers?

Signature · 2 lines
Best regards,
Artem Bityutskiy (Битюцкий Артём)