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3 Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
Oleg Nesterov
|
fb9edbe984 |
lockdep: Make held_lock->check and "int check" argument bool
The "int check" argument of lock_acquire() and held_lock->check are misleading. This is actually a boolean: 2 means "true", everything else is "false". And there is no need to pass 1 or 0 to lock_acquire() depending on CONFIG_PROVE_LOCKING, __lock_acquire() checks prove_locking at the start and clears "check" if !CONFIG_PROVE_LOCKING. Note: probably we can simply kill this member/arg. The only explicit user of check => 0 is rcu_lock_acquire(), perhaps we can change it to use lock_acquire(trylock =>, read => 2). __lockdep_no_validate means check => 0 implicitly, but we can change validate_chain() to check hlock->instance->key instead. Not to mention it would be nice to get rid of lockdep_set_novalidate_class(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Cc: Dave Jones <davej@redhat.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul McKenney <paulmck@linux.vnet.ibm.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Alan Stern <stern@rowland.harvard.edu> Cc: Sasha Levin <sasha.levin@oracle.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20140120182006.GA26495@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org> |
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Peter Hurley
|
cf872776fc |
tty: Fix hang at ldsem_down_read()
When a controlling tty is being hung up and the hang up is waiting for a just-signalled tty reader or writer to exit, and a new tty reader/writer tries to acquire an ldisc reference concurrently with the ldisc reference release from the signalled reader/writer, the hangup can hang. The new reader/writer is sleeping in ldsem_down_read() and the hangup is sleeping in ldsem_down_write() [1]. The new reader/writer fails to wakeup the waiting hangup because the wrong lock count value is checked (the old lock count rather than the new lock count) to see if the lock is unowned. Change helper function to return the new lock count if the cmpxchg was successful; document this behavior. [1] edited dmesg log from reporter SysRq : Show Blocked State task PC stack pid father systemd D ffff88040c4f0000 0 1 0 0x00000000 ffff88040c49fbe0 0000000000000046 ffff88040c4a0000 ffff88040c49ffd8 00000000001d3980 00000000001d3980 ffff88040c4a0000 ffff88040593d840 ffff88040c49fb40 ffffffff810a4cc0 0000000000000006 0000000000000023 Call Trace: [<ffffffff810a4cc0>] ? sched_clock_cpu+0x9f/0xe4 [<ffffffff810a4cc0>] ? sched_clock_cpu+0x9f/0xe4 [<ffffffff810a4cc0>] ? sched_clock_cpu+0x9f/0xe4 [<ffffffff810a4cc0>] ? sched_clock_cpu+0x9f/0xe4 [<ffffffff817a6649>] schedule+0x24/0x5e [<ffffffff817a588b>] schedule_timeout+0x15b/0x1ec [<ffffffff810a4cc0>] ? sched_clock_cpu+0x9f/0xe4 [<ffffffff817aa691>] ? _raw_spin_unlock_irq+0x24/0x26 [<ffffffff817aa10c>] down_read_failed+0xe3/0x1b9 [<ffffffff817aa26d>] ldsem_down_read+0x8b/0xa5 [<ffffffff8142b5ca>] ? tty_ldisc_ref_wait+0x1b/0x44 [<ffffffff8142b5ca>] tty_ldisc_ref_wait+0x1b/0x44 [<ffffffff81423f5b>] tty_write+0x7d/0x28a [<ffffffff814241f5>] redirected_tty_write+0x8d/0x98 [<ffffffff81424168>] ? tty_write+0x28a/0x28a [<ffffffff8115d03f>] do_loop_readv_writev+0x56/0x79 [<ffffffff8115e604>] do_readv_writev+0x1b0/0x1ff [<ffffffff8116ea0b>] ? do_vfs_ioctl+0x32a/0x489 [<ffffffff81167d9d>] ? final_putname+0x1d/0x3a [<ffffffff8115e6c7>] vfs_writev+0x2e/0x49 [<ffffffff8115e7d3>] SyS_writev+0x47/0xaa [<ffffffff817ab822>] system_call_fastpath+0x16/0x1b bash D ffffffff81c104c0 0 5469 5302 0x00000082 ffff8800cf817ac0 0000000000000046 ffff8804086b22a0 ffff8800cf817fd8 00000000001d3980 00000000001d3980 ffff8804086b22a0 ffff8800cf817a48 000000000000b9a0 ffff8800cf817a78 ffffffff81004675 ffff8800cf817a44 Call Trace: [<ffffffff81004675>] ? dump_trace+0x165/0x29c [<ffffffff810a4cc0>] ? sched_clock_cpu+0x9f/0xe4 [<ffffffff8100edda>] ? save_stack_trace+0x26/0x41 [<ffffffff817a6649>] schedule+0x24/0x5e [<ffffffff817a588b>] schedule_timeout+0x15b/0x1ec [<ffffffff810a4cc0>] ? sched_clock_cpu+0x9f/0xe4 [<ffffffff817a9f03>] ? down_write_failed+0xa3/0x1c9 [<ffffffff817aa691>] ? _raw_spin_unlock_irq+0x24/0x26 [<ffffffff817a9f0b>] down_write_failed+0xab/0x1c9 [<ffffffff817aa300>] ldsem_down_write+0x79/0xb1 [<ffffffff817aada3>] ? tty_ldisc_lock_pair_timeout+0xa5/0xd9 [<ffffffff817aada3>] tty_ldisc_lock_pair_timeout+0xa5/0xd9 [<ffffffff8142bf33>] tty_ldisc_hangup+0xc4/0x218 [<ffffffff81423ab3>] __tty_hangup+0x2e2/0x3ed [<ffffffff81424a76>] disassociate_ctty+0x63/0x226 [<ffffffff81078aa7>] do_exit+0x79f/0xa11 [<ffffffff81086bdb>] ? get_signal_to_deliver+0x206/0x62f [<ffffffff810b4bfb>] ? lock_release_holdtime.part.8+0xf/0x16e [<ffffffff81079b05>] do_group_exit+0x47/0xb5 [<ffffffff81086c16>] get_signal_to_deliver+0x241/0x62f [<ffffffff810020a7>] do_signal+0x43/0x59d [<ffffffff810f2af7>] ? __audit_syscall_exit+0x21a/0x2a8 [<ffffffff810b4bfb>] ? lock_release_holdtime.part.8+0xf/0x16e [<ffffffff81002655>] do_notify_resume+0x54/0x6c [<ffffffff817abaf8>] int_signal+0x12/0x17 Reported-by: Sami Farin <sami.farin@gmail.com> Cc: <stable@vger.kernel.org> # 3.12.x Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
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Peter Hurley
|
4898e640ca |
tty: Add timed, writer-prioritized rw semaphore
The semantics of a rw semaphore are almost ideally suited for tty line discipline lifetime management; multiple active threads obtain "references" (read locks) while performing i/o to prevent the loss or change of the current line discipline (write lock). Unfortunately, the existing rw_semaphore is ill-suited in other ways; 1) TIOCSETD ioctl (change line discipline) expects to return an error if the line discipline cannot be exclusively locked within 5 secs. Lock wait timeouts are not supported by rwsem. 2) A tty hangup is expected to halt and scrap pending i/o, so exclusive locking must be prioritized. Writer priority is not supported by rwsem. Add ld_semaphore which implements these requirements in a semantically similar way to rw_semaphore. Writer priority is handled by separate wait lists for readers and writers. Pending write waits are priortized before existing read waits and prevent further read locks. Wait timeouts are trivially added, but obviously change the lock semantics as lock attempts can fail (but only due to timeout). This implementation incorporates the write-lock stealing work of Michel Lespinasse <walken@google.com>. Cc: Michel Lespinasse <walken@google.com> Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |