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* Re: [PATCH] fs: jfs: fix a possible data race in txBegin()
@ 2020-05-04 16:15 ` Markus Elfring
  0 siblings, 0 replies; 15+ messages in thread
From: Markus Elfring @ 2020-05-04 16:15 UTC (permalink / raw)
  To: Jia-Ju Bai, jfs-discussion; +Cc: linux-kernel, kernel-janitors, Dave Kleikamp

> Thus, a data race can occur for tblk->flag.
>
> To fix this data race, the spinlock log->gclock is used in
> txBegin().
>
> This data race is found by our concurrency fuzzer.

How do you think about a wording variant like the following?

   Change description:
   A data race can occur for the data structure member “flag”.
   This data race was found by our concurrency fuzzer.

   Thus use the spin lock “gclock” for the resetting of five
   data structure members in this function implementation.


Would you like to add the tag “Fixes” to the commit message?

Regards,
Markus

^ permalink raw reply	[flat|nested] 15+ messages in thread
* Re: [PATCH] fs: jfs: fix a possible data race in metapage_writepage()
  2020-05-04 16:15 ` Markus Elfring
@ 2020-05-04 16:33 ` Markus Elfring
  -1 siblings, 0 replies; 15+ messages in thread
From: Markus Elfring @ 2020-05-04 16:33 UTC (permalink / raw)
  To: Jia-Ju Bai, jfs-discussion; +Cc: linux-kernel, kernel-janitors, Dave Kleikamp

…
> To fix this data race, the spinlock mp->log->gclock is used in
> metapage_writepage().
>
> This data race is found by our concurrency fuzzer.

How do you think about a wording variant like the following?

   Change description:
   …
   This data race was found by our concurrency fuzzer.

   Thus use the spin lock “mp->log->gclock” for the assignment of
   the data structure member “log->cflag” to a local variable
   in this function implementation.


Would you like to add the tag “Fixes” to the commit message?

Regards,
Markus

^ permalink raw reply	[flat|nested] 15+ messages in thread
* [PATCH] fs: jfs: fix a possible data race in txBegin()
@ 2020-05-04 15:34 Jia-Ju Bai
  0 siblings, 0 replies; 15+ messages in thread
From: Jia-Ju Bai @ 2020-05-04 15:34 UTC (permalink / raw)
  To: shaggy; +Cc: jfs-discussion, linux-kernel, Jia-Ju Bai

The functions txBegin() and txLazyCommit() can be concurrently executed
in the following call contexts:

Thread1:
  jfs_write_inode()
    jfs_commit_inode()
      txBegin()

Thread2:
  jfs_lazycommit()
    txLazyCommit()

In txBegin():
  tblk->next = tblk->last = tblk->xflag = tblk->flag = tblk->lsn = 0;

In txLazyCommit():
  spin_lock_irq(&log->gclock);
  ...
  tblk->flag |= tblkGC_COMMITTED;
  ...
  spin_unlock_irq(&log->gclock);

Thus, a data race can occur for tblk->flag.

To fix this data race, the spinlock log->gclock is used in 
txBegin().

This data race is found by our concurrency fuzzer.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
---
 fs/jfs/jfs_txnmgr.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/jfs/jfs_txnmgr.c b/fs/jfs/jfs_txnmgr.c
index c8ce7f1bc594..a1f124aad2e0 100644
--- a/fs/jfs/jfs_txnmgr.c
+++ b/fs/jfs/jfs_txnmgr.c
@@ -415,7 +415,9 @@ tid_t txBegin(struct super_block *sb, int flag)
 	 *
 	 * memset(tblk, 0, sizeof(struct tblock));
 	 */
+	spin_lock_irq(&log->gclock);
 	tblk->next = tblk->last = tblk->xflag = tblk->flag = tblk->lsn = 0;
+	spin_unlock_irq(&log->gclock);
 
 	tblk->sb = sb;
 	++log->logtid;
-- 
2.17.1


^ permalink raw reply related	[flat|nested] 15+ messages in thread
end of thread, other threads:[~2020-05-05 13:48 UTC | newest]

Thread overview: 15+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-05-04 16:15 [PATCH] fs: jfs: fix a possible data race in txBegin() Markus Elfring
2020-05-04 16:15 ` Markus Elfring
2020-05-05  4:10 ` Jia-Ju Bai
2020-05-05  4:10   ` Jia-Ju Bai
2020-05-05  5:12   ` Markus Elfring
2020-05-05  5:12     ` Markus Elfring
2020-05-05 13:04     ` Jia-Ju Bai
2020-05-05 13:04       ` Jia-Ju Bai
2020-05-05 13:23     ` Dave Kleikamp
2020-05-05 13:23       ` Dave Kleikamp
2020-05-05 13:32       ` Jia-Ju Bai
2020-05-05 13:32         ` Jia-Ju Bai
  -- strict thread matches above, loose matches on Subject: below --
2020-05-04 16:33 [PATCH] fs: jfs: fix a possible data race in metapage_writepage() Markus Elfring
2020-05-04 16:33 ` Markus Elfring
2020-05-04 15:34 [PATCH] fs: jfs: fix a possible data race in txBegin() Jia-Ju Bai

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