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Fri, 14 Mar 2025 09:27:13 +0000 (GMT) Message-ID: <333198fd-e028-42cb-8847-bd5ddd2a623b@linux.ibm.com> Date: Fri, 14 Mar 2025 14:57:13 +0530 X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 4/6] powerpc: book3s: vas: use lock guard for mutex To: Peter Zijlstra Cc: maddy@linux.ibm.com, linuxppc-dev@lists.ozlabs.org, npiggin@gmail.com, christophe.leroy@csgroup.eu, mpe@ellerman.id.au, fbarrat@linux.ibm.com, ajd@linux.ibm.com, mahesh@linux.ibm.com, oohall@gmail.com, hbathini@linux.ibm.com, dhowells@redhat.com, haren@linux.ibm.com, linux-kernel@vger.kernel.org References: <20250314054544.1998928-1-sshegde@linux.ibm.com> <20250314054544.1998928-5-sshegde@linux.ibm.com> <20250314082527.GU5880@noisy.programming.kicks-ass.net> From: Shrikanth Hegde Content-Language: en-US In-Reply-To: <20250314082527.GU5880@noisy.programming.kicks-ass.net> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: bhqGI1arLrSR6zhLyvrGoDlQ2tlLnGbB X-Proofpoint-ORIG-GUID: Pq9BzbBph-GplGKCkLgSvvH7E4Ys25bm X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1093,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-03-14_03,2025-03-13_01,2024-11-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 spamscore=0 malwarescore=0 impostorscore=0 priorityscore=1501 bulkscore=0 phishscore=0 lowpriorityscore=0 suspectscore=0 mlxlogscore=896 clxscore=1015 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2502280000 definitions=main-2503140075 On 3/14/25 13:55, Peter Zijlstra wrote: > On Fri, Mar 14, 2025 at 11:15:42AM +0530, Shrikanth Hegde wrote: >> use guard(mutex) for scope based resource management of mutex. >> This would make the code simpler and easier to maintain. >> >> More details on lock guards can be found at >> https://lore.kernel.org/all/20230612093537.614161713@infradead.org/T/#u >> >> There is also an example of using scoped_guard. >> >> Signed-off-by: Shrikanth Hegde >> --- >> arch/powerpc/platforms/book3s/vas-api.c | 19 ++++++------------- >> 1 file changed, 6 insertions(+), 13 deletions(-) >> >> diff --git a/arch/powerpc/platforms/book3s/vas-api.c b/arch/powerpc/platforms/book3s/vas-api.c >> index 0b6365d85d11..eb1a97271afb 100644 >> --- a/arch/powerpc/platforms/book3s/vas-api.c >> +++ b/arch/powerpc/platforms/book3s/vas-api.c >> @@ -425,7 +425,7 @@ static vm_fault_t vas_mmap_fault(struct vm_fault *vmf) >> return VM_FAULT_SIGBUS; >> } >> >> - mutex_lock(&txwin->task_ref.mmap_mutex); >> + guard(mutex)(&txwin->task_ref.mmap_mutex); >> /* >> * The window may be inactive due to lost credit (Ex: core >> * removal with DLPAR). If the window is active again when >> @@ -437,11 +437,9 @@ static vm_fault_t vas_mmap_fault(struct vm_fault *vmf) >> if (paste_addr) { >> fault = vmf_insert_pfn(vma, vma->vm_start, >> (paste_addr >> PAGE_SHIFT)); >> - mutex_unlock(&txwin->task_ref.mmap_mutex); >> return fault; >> } >> } >> - mutex_unlock(&txwin->task_ref.mmap_mutex); > > I had to open up this file to check, but this seems incorrect since you > now also run do_fail_paste() with the lock held, where previously you > did not. > Yes. Got it. let me use scoped_guard for it as well. There is get_user and other things in the fail parse and having it with mutex will not be good. I went through the rest of the patches too. It is mostly return after mutex. Only in Patch 5/6 there is additional debug statement. Let me put a comment there. > >> /* >> * Received this fault due to closing the actual window.