rpc_wait_bit_killable() is called when it is appropriate for a fatal signal to abort the wait. If it is called late during process exit after exit_signals() is called (and when PF_EXITING is set), it cannot receive a fatal signal so waiting indefinitely is not safe. However aborting immediately, as it currently does, is not ideal as it mean that the related NFS request cannot succeed, even if the network and server are working properly. One of the causes of filesystem IO when PF_EXITING is set is acct_process() which may access the process accounting file. For a NFS-root configuration, this can be accessed over NFS. In this configuration LTP test "acct02" fails. Though waiting indefinitely is not appropriate, aborting immediately is also not desirable. This patch aims for a middle ground of waiting at most 5 seconds. This should be enough when NFS service is working, but not so much as to delay process exit excessively when NFS service is not functioning. Reported-by: Mark Brown <broonie@xxxxxxxxxx> Reported-and-tested-by: Harshvardhan Jha <harshvardhan.j.jha@xxxxxxxxxx> Link: https://lore.kernel.org/linux-nfs/7d4d57b0-39a3-49f1-8ada-60364743e3b4@xxxxxxxxxxxxx/ Fixes: 14e41b16e8cb ("SUNRPC: Don't allow waiting for exiting tasks") Signed-off-by: NeilBrown <neil@xxxxxxxxxx> --- net/sunrpc/sched.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c index 73bc39281ef5..92f39e828fbe 100644 --- a/net/sunrpc/sched.c +++ b/net/sunrpc/sched.c @@ -276,11 +276,15 @@ EXPORT_SYMBOL_GPL(rpc_destroy_wait_queue); static int rpc_wait_bit_killable(struct wait_bit_key *key, int mode) { - if (unlikely(current->flags & PF_EXITING)) - return -EINTR; - schedule(); - if (signal_pending_state(mode, current)) - return -ERESTARTSYS; + if (unlikely(current->flags & PF_EXITING)) { + /* Cannot be killed by a signal, so don't wait indefinitely */ + if (schedule_timeout(5 * HZ) == 0) + return -EINTR; + } else { + schedule(); + if (signal_pending_state(mode, current)) + return -ERESTARTSYS; + } return 0; } -- 2.50.0.107.gf914562f5916.dirty
