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| author | Carlos Llamas <cmllamas@google.com> | 2024-07-11 20:14:51 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2024-07-12 11:31:37 +0200 |
| commit | 31643d84b8c3d9c846aa0e20bc033e46c68c7e7d (patch) | |
| tree | 65c9b870d4072d926e72bca7ddea6ffffd43d575 | |
| parent | a5e43e2d202de39196de9fba689c34f8270782eb (diff) | |
| download | lwn-31643d84b8c3d9c846aa0e20bc033e46c68c7e7d.tar.gz lwn-31643d84b8c3d9c846aa0e20bc033e46c68c7e7d.zip | |
binder: fix hang of unregistered readers
With the introduction of binder_available_for_proc_work_ilocked() in
commit 1b77e9dcc3da ("ANDROID: binder: remove proc waitqueue") a binder
thread can only "wait_for_proc_work" after its thread->looper has been
marked as BINDER_LOOPER_STATE_{ENTERED|REGISTERED}.
This means an unregistered reader risks waiting indefinitely for work
since it never gets added to the proc->waiting_threads. If there are no
further references to its waitqueue either the task will hang. The same
applies to readers using the (e)poll interface.
I couldn't find the rationale behind this restriction. So this patch
restores the previous behavior of allowing unregistered threads to
"wait_for_proc_work". Note that an error message for this scenario,
which had previously become unreachable, is now re-enabled.
Fixes: 1b77e9dcc3da ("ANDROID: binder: remove proc waitqueue")
Cc: stable@vger.kernel.org
Cc: Martijn Coenen <maco@google.com>
Cc: Arve Hjønnevåg <arve@google.com>
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Link: https://lore.kernel.org/r/20240711201452.2017543-1-cmllamas@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/android/binder.c | 4 |
1 files changed, 1 insertions, 3 deletions
diff --git a/drivers/android/binder.c b/drivers/android/binder.c index 0c2161b1f057..f26286e3713e 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -570,9 +570,7 @@ static bool binder_has_work(struct binder_thread *thread, bool do_proc_work) static bool binder_available_for_proc_work_ilocked(struct binder_thread *thread) { return !thread->transaction_stack && - binder_worklist_empty_ilocked(&thread->todo) && - (thread->looper & (BINDER_LOOPER_STATE_ENTERED | - BINDER_LOOPER_STATE_REGISTERED)); + binder_worklist_empty_ilocked(&thread->todo); } static void binder_wakeup_poll_threads_ilocked(struct binder_proc *proc, |