glibc: nptl Update comments and indentation for new condvar implementation

The following commits have been cherry-picked from Glibc master branch:
Bug : https://sourceware.org/bugzilla/show_bug.cgi?id=25847

Upstream-Status: Backport
[https://sourceware.org/git/?p=glibc.git;a=commit;h=0cc973160c23bb67f895bc887dd6942d29f8fee3]

(From OE-Core rev: e5296415e97e4d704c4c8d11ad243061a1e14997)

Signed-off-by: Sunil Dora <sunilkumar.dora@windriver.com>
Signed-off-by: Steve Sakoman <steve@sakoman.com>

2 files changed, 145 insertions, 0 deletions

diff --git a/meta/recipes-core/glibc/glibc/0026-PR25847-2.patch b/meta/recipes-core/glibc/glibc/0026-PR25847-2.patch
new file mode 100644
index 0000000000..cb89431769
--- /dev/null
+++ b/meta/recipes-core/glibc/glibc/0026-PR25847-2.patch
@@ -0,0 +1,144 @@
+From 6aab1191e35a3da66e8c49d95178a9d77c119a1f Mon Sep 17 00:00:00 2001
+From: Malte Skarupke <malteskarupke@fastmail.fm>
+Date: Mon, 16 Jun 2025 23:17:53 -0700
+Subject: [PATCH] nptl: Update comments and indentation for new condvar
+ implementation
+
+Some comments were wrong after the most recent commit. This fixes that.
+Also fixing indentation where it was using spaces instead of tabs.
+
+The following commits have been cherry-picked from Glibc master branch:
+Bug : https://sourceware.org/bugzilla/show_bug.cgi?id=25847
+
+Upstream-Status: Backport
+[https://sourceware.org/git/?p=glibc.git;a=commit;h=0cc973160c23bb67f895bc887dd6942d29f8fee3]
+
+Signed-off-by: Sunil Dora <sunilkumar.dora@windriver.com>
+---
+ nptl/pthread_cond_common.c |  5 +++--
+ nptl/pthread_cond_wait.c   | 39 +++++++++++++++++++-------------------
+ 2 files changed, 22 insertions(+), 22 deletions(-)
+
+diff --git a/nptl/pthread_cond_common.c b/nptl/pthread_cond_common.c
+index 8dd7037923..306a207dd6 100644
+--- a/nptl/pthread_cond_common.c
++++ b/nptl/pthread_cond_common.c
+@@ -221,8 +221,9 @@ __condvar_quiesce_and_switch_g1 (pthread_cond_t *cond, uint64_t wseq,
+      * New waiters arriving concurrently with the group switching will all go
+        into G2 until we atomically make the switch.  Waiters existing in G2
+        are not affected.
+-     * Waiters in G1 will be closed out immediately by the advancing of
+-       __g_signals to the next "lowseq" (low 31 bits of the new g1_start),
++     * Waiters in G1 have already received a signal and been woken. If they
++       haven't woken yet, they will be closed out immediately by the advancing
++       of __g_signals to the next "lowseq" (low 31 bits of the new g1_start),
+        which will prevent waiters from blocking using a futex on
+        __g_signals since it provides enough signals for all possible
+        remaining waiters.  As a result, they can each consume a signal
+diff --git a/nptl/pthread_cond_wait.c b/nptl/pthread_cond_wait.c
+index 1cb3dbf7b0..cee1968756 100644
+--- a/nptl/pthread_cond_wait.c
++++ b/nptl/pthread_cond_wait.c
+@@ -249,7 +249,7 @@ __condvar_cleanup_waiting (void *arg)
+    figure out whether they are in a group that has already been completely
+    signaled (i.e., if the current G1 starts at a later position that the
+    waiter's position).  Waiters cannot determine whether they are currently
+-   in G2 or G1 -- but they do not have too because all they are interested in
++   in G2 or G1 -- but they do not have to because all they are interested in
+    is whether there are available signals, and they always start in G2 (whose
+    group slot they know because of the bit in the waiter sequence.  Signalers
+    will simply fill the right group until it is completely signaled and can
+@@ -412,7 +412,7 @@ __pthread_cond_wait_common (pthread_cond_t *cond, pthread_mutex_t *mutex,
+     }
+ 
+   /* Now wait until a signal is available in our group or it is closed.
+-     Acquire MO so that if we observe a value of zero written after group
++     Acquire MO so that if we observe (signals == lowseq) after group
+      switching in __condvar_quiesce_and_switch_g1, we synchronize with that
+      store and will see the prior update of __g1_start done while switching
+      groups too.  */
+@@ -422,8 +422,8 @@ __pthread_cond_wait_common (pthread_cond_t *cond, pthread_mutex_t *mutex,
+     {
+       while (1)
+        {
+-          uint64_t g1_start = __condvar_load_g1_start_relaxed (cond);
+-          unsigned int lowseq = (g1_start & 1) == g ? signals : g1_start & ~1U;
++         uint64_t g1_start = __condvar_load_g1_start_relaxed (cond);
++         unsigned int lowseq = (g1_start & 1) == g ? signals : g1_start & ~1U;
+ 
+          /* Spin-wait first.
+             Note that spinning first without checking whether a timeout
+@@ -447,21 +447,21 @@ __pthread_cond_wait_common (pthread_cond_t *cond, pthread_mutex_t *mutex,
+ 
+              /* Reload signals.  See above for MO.  */
+              signals = atomic_load_acquire (cond->__data.__g_signals + g);
+-              g1_start = __condvar_load_g1_start_relaxed (cond);
+-              lowseq = (g1_start & 1) == g ? signals : g1_start & ~1U;
++             g1_start = __condvar_load_g1_start_relaxed (cond);
++             lowseq = (g1_start & 1) == g ? signals : g1_start & ~1U;
+              spin--;
+            }
+ 
+-          if (seq < (g1_start >> 1))
++         if (seq < (g1_start >> 1))
+            {
+-              /* If the group is closed already,
++             /* If the group is closed already,
+                 then this waiter originally had enough extra signals to
+                 consume, up until the time its group was closed.  */
+               goto done;
+-            }
++           }
+ 
+          /* If there is an available signal, don't block.
+-             If __g1_start has advanced at all, then we must be in G1
++            If __g1_start has advanced at all, then we must be in G1
+             by now, perhaps in the process of switching back to an older
+             G2, but in either case we're allowed to consume the available
+             signal and should not block anymore.  */
+@@ -483,22 +483,23 @@ __pthread_cond_wait_common (pthread_cond_t *cond, pthread_mutex_t *mutex,
+             sequence.  */
+          atomic_fetch_add_acquire (cond->__data.__g_refs + g, 2);
+          signals = atomic_load_acquire (cond->__data.__g_signals + g);
+-          g1_start = __condvar_load_g1_start_relaxed (cond);
+-          lowseq = (g1_start & 1) == g ? signals : g1_start & ~1U;
++         g1_start = __condvar_load_g1_start_relaxed (cond);
++         lowseq = (g1_start & 1) == g ? signals : g1_start & ~1U;
+ 
+-          if (seq < (g1_start >> 1))
++         if (seq < (g1_start >> 1))
+            {
+-              /* group is closed already, so don't block */
++             /* group is closed already, so don't block */
+              __condvar_dec_grefs (cond, g, private);
+              goto done;
+            }
+ 
+          if ((int)(signals - lowseq) >= 2)
+            {
+-             /* a signal showed up or G1/G2 switched after we grabbed the refcount */
++             /* a signal showed up or G1/G2 switched after we grabbed the
++                refcount */
+              __condvar_dec_grefs (cond, g, private);
+              break;
+-            }
++           }
+ 
+          // Now block.
+          struct _pthread_cleanup_buffer buffer;
+@@ -536,10 +537,8 @@ __pthread_cond_wait_common (pthread_cond_t *cond, pthread_mutex_t *mutex,
+        if (seq < (__condvar_load_g1_start_relaxed (cond) >> 1))
+         goto done;
+     }
+-  /* Try to grab a signal.  Use acquire MO so that we see an up-to-date value
+-     of __g1_start below (see spinning above for a similar case).  In
+-     particular, if we steal from a more recent group, we will also see a
+-     more recent __g1_start below.  */
++  /* Try to grab a signal.  See above for MO.  (if we do another loop
++     iteration we need to see the correct value of g1_start)  */
+   while (!atomic_compare_exchange_weak_acquire (cond->__data.__g_signals + g,
+                                                &signals, signals - 2));
+ 
+-- 
+2.49.0
+
diff --git a/meta/recipes-core/glibc/glibc_2.35.bb b/meta/recipes-core/glibc/glibc_2.35.bb
index f15e031971..92c4dad023 100644
--- a/meta/recipes-core/glibc/glibc_2.35.bb
+++ b/meta/recipes-core/glibc/glibc_2.35.bb
@@ -63,6 +63,7 @@ SRC_URI =  "${GLIBC_GIT_URI};branch=${SRCBRANCH};name=glibc \
            file://0024-fix-create-thread-failed-in-unprivileged-process-BZ-.patch \
            file://0025-CVE-2025-4802.patch \
            file://0026-PR25847-1.patch \
+           file://0026-PR25847-2.patch \
            \
            file://0001-Revert-Linux-Implement-a-useful-version-of-_startup_.patch \
            file://0002-get_nscd_addresses-Fix-subscript-typos-BZ-29605.patch \