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authorMaurizio Lombardi <mlombard@redhat.com>2020-03-13 20:06:55 +0300
committerMartin K. Petersen <martin.petersen@oracle.com>2020-03-27 04:47:47 +0300
commit57c46e9f33da530a2485fa01aa27b6d18c28c796 (patch)
treedaf385a074eb7da740d2ad327124611ac9908cb3 /include/target
parente49a7d994379278d3353d7ffc7994672752fb0ad (diff)
downloadlinux-57c46e9f33da530a2485fa01aa27b6d18c28c796.tar.xz
scsi: target: fix hang when multiple threads try to destroy the same iscsi session
A number of hangs have been reported against the target driver; they are due to the fact that multiple threads may try to destroy the iscsi session at the same time. This may be reproduced for example when a "targetcli iscsi/iqn.../tpg1 disable" command is executed while a logout operation is underway. When this happens, two or more threads may end up sleeping and waiting for iscsit_close_connection() to execute "complete(session_wait_comp)". Only one of the threads will wake up and proceed to destroy the session structure, the remaining threads will hang forever. Note that if the blocked threads are somehow forced to wake up with complete_all(), they will try to free the same iscsi session structure destroyed by the first thread, causing double frees, memory corruptions etc... With this patch, the threads that want to destroy the iscsi session will increase the session refcount and will set the "session_close" flag to 1; then they wait for the driver to close the remaining active connections. When the last connection is closed, iscsit_close_connection() will wake up all the threads and will wait for the session's refcount to reach zero; when this happens, iscsit_close_connection() will destroy the session structure because no one is referencing it anymore. INFO: task targetcli:5971 blocked for more than 120 seconds. Tainted: P OE 4.15.0-72-generic #81~16.04.1 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. targetcli D 0 5971 1 0x00000080 Call Trace: __schedule+0x3d6/0x8b0 ? vprintk_func+0x44/0xe0 schedule+0x36/0x80 schedule_timeout+0x1db/0x370 ? __dynamic_pr_debug+0x8a/0xb0 wait_for_completion+0xb4/0x140 ? wake_up_q+0x70/0x70 iscsit_free_session+0x13d/0x1a0 [iscsi_target_mod] iscsit_release_sessions_for_tpg+0x16b/0x1e0 [iscsi_target_mod] iscsit_tpg_disable_portal_group+0xca/0x1c0 [iscsi_target_mod] lio_target_tpg_enable_store+0x66/0xe0 [iscsi_target_mod] configfs_write_file+0xb9/0x120 __vfs_write+0x1b/0x40 vfs_write+0xb8/0x1b0 SyS_write+0x5c/0xe0 do_syscall_64+0x73/0x130 entry_SYSCALL_64_after_hwframe+0x3d/0xa2 Link: https://lore.kernel.org/r/20200313170656.9716-3-mlombard@redhat.com Reported-by: Matt Coleman <mcoleman@datto.com> Tested-by: Matt Coleman <mcoleman@datto.com> Tested-by: Rahul Kundu <rahul.kundu@chelsio.com> Signed-off-by: Maurizio Lombardi <mlombard@redhat.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Diffstat (limited to 'include/target')
-rw-r--r--include/target/iscsi/iscsi_target_core.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/include/target/iscsi/iscsi_target_core.h b/include/target/iscsi/iscsi_target_core.h
index a49d37140a64..591cd9e4692c 100644
--- a/include/target/iscsi/iscsi_target_core.h
+++ b/include/target/iscsi/iscsi_target_core.h
@@ -676,7 +676,7 @@ struct iscsi_session {
atomic_t session_logout;
atomic_t session_reinstatement;
atomic_t session_stop_active;
- atomic_t sleep_on_sess_wait_comp;
+ atomic_t session_close;
/* connection list */
struct list_head sess_conn_list;
struct list_head cr_active_list;