From: Tariq Saeed Date: Mon, 23 Jun 2014 20:22:08 +0000 (-0700) Subject: ocfs2: fix deadlock when two nodes are converting same lock from PR to EX and idletim... X-Git-Tag: omap-for-v3.16/fixes-rc4~63^2~7 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=27bf6305cf85cb474295c300c99cc3d10d68f50a;p=pandora-kernel.git ocfs2: fix deadlock when two nodes are converting same lock from PR to EX and idletimeout closes conn Orabug: 18639535 Two node cluster and both nodes hold a lock at PR level and both want to convert to EX at the same time. Master node 1 has sent BAST and then closes the connection due to idletime out. Node 0 receives BAST, sends unlock req with cancel flag but gets error -ENOTCONN. The problem is this error is ignored in dlm_send_remote_unlock_request() on the **incorrect** assumption that the master is dead. See NOTE in comment why it returns DLM_NORMAL. Upon getting DLM_NORMAL, node 0 proceeds to sends convert (without cancel flg) which fails with -ENOTCONN. waits 5 sec and resends. This time gets DLM_IVLOCKID from the master since lock not found in grant, it had been moved to converting queue in response to conv PR->EX req. No way out. Node 1 (master) Node 0 ============== ====== lock mode PR PR convert PR -> EX mv grant -> convert and que BAST ... <-------- convert PR -> EX convert que looks like this: ((node 1, PR -> EX) (node 0, PR -> EX)) ... BAST (want PR -> NL) ------------------> ... idle timout, conn closed ... In response to BAST, sends unlock with cancel convert flag gets -ENOTCONN. Ignores and sends remote convert request gets -ENOTCONN, waits 5 Sec, retries ... reconnects <----------------- convert req goes through on next try does not find lock on grant que status DLM_IVLOCKID ------------------> ... No way out. Fix is to keep retrying unlock with cancel flag until it succeeds or the master dies. Signed-off-by: Tariq Saeed Reviewed-by: Mark Fasheh Cc: Joel Becker Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Reading git-diff-tree failed