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Mon, 6 Jul 2026 14:16:08 +0000 (GMT) From: Nilay Shroff To: linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org Cc: hch@lst.de, elver@google.com, kbusch@kernel.org, sagi@grimberg.me, axboe@fb.com, bvanassche@acm.org, gjoyce@linux.ibm.com, Nilay Shroff Subject: [PATCH v3 14/18] list: Permit context-unguarded access with list_empty_careful() Date: Mon, 6 Jul 2026 19:44:16 +0530 Message-ID: <20260706141452.3008233-15-nilay@linux.ibm.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260706141452.3008233-1-nilay@linux.ibm.com> References: <20260706141452.3008233-1-nilay@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-GUID: zExdXhfxLOdQT3ZahkjvEZVbsUZbgkvp X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzA2MDE0MSBTYWx0ZWRfX5NWPkmFoGH36 YXVctFggdQgTMiSh56FSUTUu8V3xrR4JBCA7lS5JvSAo4oBQjzQH8iE/Kx8m5gZwfTaqyDAUBr7 IV7d/Wica/qsCXyE9cPIDTyqg0umftYO0Bj5NYkZ9fUWsULFEfGBK4yT+Y3qbrwdIgKhs+yKEXC nCNLK8gwnE4RAzCMp8kCYJnQR6mWN02brY7YbbaVJvtVNnaTje6l8einLaj3AgPbgnblSHigY45 iy0N7rTpQ3rnPmub7xBd5v8UvC8cLzo4+ZqdLCqtiYMs9HS/eDmvb/TltKWvILbPImh36y/HoYi Q3f6vgUPgWprc55DsTOpN3VeTM+xLT405FKKtq1ycTGpJtMcF+dBAPCJC9hDAB/+8Taf2h8Wk6Q jf+XPIQZW1gdcAT6pV1wbUXHdIfPn492+WyM7DB1geTInL7CzLRpQrb/728CrflxR1qDuWaTmcn mR1YiasCxGQz2T8A2LQ== X-Proofpoint-ORIG-GUID: UI6wjm6m7F984Ph73J_QMP7O5GC2w4Gy X-Authority-Analysis: v=2.4 cv=FqQ1OWrq c=1 sm=1 tr=0 ts=6a4bb8b0 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=RAioF0-LDSMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=1XWaLZrsAAAA:8 a=VnNF1IyMAAAA:8 a=4at8UNLr3tDfbFC0C8MA:9 X-Proofpoint-Spam-Info: AW1haW4tMjYwNzA2MDE0MSBTYWx0ZWRfXzJeosjubft43 rkP6NZx4jynuBKJ3J084UQXxHfN+858mX70KiF/vVwmU8LCn3WMCs/9VD7y/EYVIH+6w1iarMub Cxveo+WIalZennUIp/dSxHHvtXz1sTI= X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-07-06_01,2026-07-06_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 impostorscore=0 clxscore=1015 malwarescore=0 lowpriorityscore=0 priorityscore=1501 bulkscore=0 suspectscore=0 spamscore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607060141 From: Marco Elver With Context Analysis (viz. Clang's Thread Safety Analysis), list_heads that are __guarded_by(..) require holding the appropriate context lock when accessing and manipulating them via the list API. Because Clang's warning diagnostics do not perform inter-procedural analysis, this is enforced by Clang with -Wthread-safety-pointer in the caller at the call boundary; a warning is produced when passing a pointer to a guarded variable without holding the appropriate context locks: warning: passing pointer to variable 'list' requires holding [...] [-Wthread-safety-pointer] if (list_empty(&ctrl->list)) An exception is list_empty_careful(), which is like list_empty(), except that it is permitted to use without holding any context lock (carefully). Mark list_empty_careful() __context_unsafe, which disables context analysis within list_empty_careful(), but also suppresses warnings generated in callers related to its pointer arguments. Signed-off-by: Marco Elver Signed-off-by: Nilay Shroff --- include/linux/list.h | 1 + 1 file changed, 1 insertion(+) diff --git a/include/linux/list.h b/include/linux/list.h index f6f22c8b06f7..19212bfc3f6d 100644 --- a/include/linux/list.h +++ b/include/linux/list.h @@ -444,6 +444,7 @@ static inline void list_del_init_careful(struct list_head *entry) * if another CPU could re-list_add() it. */ static inline int list_empty_careful(const struct list_head *head) + __context_unsafe(/* intentional lockless access to @head */) { struct list_head *next = smp_load_acquire(&head->next); return list_is_head(next, head) && (next == READ_ONCE(head->prev)); -- 2.53.0