git: ba77290cceac - stable/13 - linux(4): Handle cas failure on ll/sc operations

The branch stable/13 has been updated by dchagin:

URL: https://cgit.FreeBSD.org/src/commit/?id=ba77290cceac3391aa4a3469725e093fb1366fe1

commit ba77290cceac3391aa4a3469725e093fb1366fe1
Author:     Dmitry Chagin <dchagin@FreeBSD.org>
AuthorDate: 2022-05-19 16:52:18 +0000
Commit:     Dmitry Chagin <dchagin@FreeBSD.org>
CommitDate: 2022-06-17 19:35:25 +0000

    linux(4): Handle cas failure on ll/sc operations
    
    Follow the 11a6ecd4. Check and handle the case when the ll/sc casu fails
    even when the compare succeeds.
    
    For more details PR/263825, https://reviews.freebsd.org/D35150.
    
    Obtained from:          Andrew@
    MFC after:              2 weeks
    
    (cherry picked from commit 2cd662064a0cd8d179cbb5a06378fce0ec458747)
---
 sys/compat/linux/linux_futex.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/sys/compat/linux/linux_futex.c b/sys/compat/linux/linux_futex.c
index 6825d13e1aab..8bcdc378cf70 100644
--- a/sys/compat/linux/linux_futex.c
+++ b/sys/compat/linux/linux_futex.c
@@ -410,6 +410,17 @@ linux_futex_lock_pi(struct thread *td, bool try, struct linux_futex_args *args)
 			break;
 		}
 
+		/*
+		 * Nobody owns it, but the acquire failed. This can happen
+		 * with ll/sc atomic.
+		 */
+		if (owner == 0) {
+			error = thread_check_susp(td, true);
+			if (error != 0)
+				break;
+			continue;
+		}
+
 		/*
 		 * Avoid overwriting a possible error from sleep due
 		 * to the pending signal with suspension check result.