Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752443AbdHPRkd (ORCPT ); Wed, 16 Aug 2017 13:40:33 -0400 Received: from mail.skyhub.de ([5.9.137.197]:34666 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752120AbdHPRkb (ORCPT ); Wed, 16 Aug 2017 13:40:31 -0400 Date: Wed, 16 Aug 2017 19:40:28 +0200 From: Borislav Petkov To: "Kani, Toshimitsu" Cc: "linux-kernel@vger.kernel.org" , "rostedt@goodmis.org" , "mchehab@kernel.org" , "rjw@rjwysocki.net" , "tony.luck@intel.com" , "lenb@kernel.org" , "linux-acpi@vger.kernel.org" , "linux-edac@vger.kernel.org" Subject: Re: [PATCH v2 4/7] ghes_edac: avoid multiple calls to dmi_walk() Message-ID: <20170816174028.dqfvubjigvwtcbcy@pd.tnic> References: <1502736750.2042.145.camel@hpe.com> <20170814193432.mjldfhfal5ba5dt7@pd.tnic> <1502741290.2042.147.camel@hpe.com> <20170814203942.6t3mrq3hc324blab@pd.tnic> <1502810766.2042.149.camel@hpe.com> <20170815154815.wy3dqwb4yi3feahg@intel.com> <20170816082931.p6rpvtlxwt5nccxr@pd.tnic> <1502896578.2042.155.camel@hpe.com> <20170816164234.mgwapenb7fpym6nk@pd.tnic> <1502903940.2042.157.camel@hpe.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1502903940.2042.157.camel@hpe.com> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7114 Lines: 220 On Wed, Aug 16, 2017 at 05:28:50PM +0000, Kani, Toshimitsu wrote: > Assuming this big spinlock works, yes, this addresses my concern that You mean, lengthy locked section. We can always switch to on-stack buffers if there are issues or even to something more fancy like genpool. > I will test the patch with an SCI when I got a chance. I won't be able > to test other notification types or race conditions, though. Thanks, here's the latest version with the atomic registration too. --- drivers/edac/ghes_edac.c | 116 +++++++++++++++++++++-------------------------- 1 file changed, 51 insertions(+), 65 deletions(-) diff --git a/drivers/edac/ghes_edac.c b/drivers/edac/ghes_edac.c index 6f80eb65c26c..386e04a7bda0 100644 --- a/drivers/edac/ghes_edac.c +++ b/drivers/edac/ghes_edac.c @@ -28,10 +28,15 @@ struct ghes_edac_pvt { char msg[80]; }; -static LIST_HEAD(ghes_reglist); -static DEFINE_MUTEX(ghes_edac_lock); -static int ghes_edac_mc_num; +static atomic_t ghes_init = ATOMIC_INIT(0); +static struct ghes_edac_pvt *ghes_pvt; +/* + * Sync with other, potentially concurrent callers of + * ghes_edac_report_mem_error(). We don't know what the + * "inventive" firmware would do. + */ +static DEFINE_SPINLOCK(ghes_lock); /* Memory Device - Type 17 of SMBIOS spec */ struct memdev_dmi_entry { @@ -169,18 +174,26 @@ void ghes_edac_report_mem_error(struct ghes *ghes, int sev, enum hw_event_mc_err_type type; struct edac_raw_error_desc *e; struct mem_ctl_info *mci; - struct ghes_edac_pvt *pvt = NULL; + struct ghes_edac_pvt *pvt = ghes_pvt; + unsigned long flags; char *p; u8 grain_bits; - list_for_each_entry(pvt, &ghes_reglist, list) { - if (ghes == pvt->ghes) - break; - } if (!pvt) { pr_err("Internal error: Can't find EDAC structure\n"); return; } + + /* + * We can do the locking below because GHES defers error processing + * from NMI to IRQ context. Whenever that changes, we'd at least + * know. + */ + if (WARN_ON_ONCE(in_nmi())) + return; + + spin_lock_irqsave(&ghes_lock, flags); + mci = pvt->mci; e = &mci->error_desc; @@ -398,8 +411,8 @@ void ghes_edac_report_mem_error(struct ghes *ghes, int sev, (e->page_frame_number << PAGE_SHIFT) | e->offset_in_page, grain_bits, e->syndrome, pvt->detail_location); - /* Report the error via EDAC API */ edac_raw_mc_handle_error(type, mci, e); + spin_unlock_irqrestore(&ghes_lock, flags); } EXPORT_SYMBOL_GPL(ghes_edac_report_mem_error); @@ -409,9 +422,14 @@ int ghes_edac_register(struct ghes *ghes, struct device *dev) int rc, num_dimm = 0; struct mem_ctl_info *mci; struct edac_mc_layer layers[1]; - struct ghes_edac_pvt *pvt; struct ghes_edac_dimm_fill dimm_fill; + /* + * We have only one logical memory controller to which all DIMMs belong. + */ + if (atomic_inc_return(&ghes_init) > 1) + return 0; + /* Get the number of DIMMs */ dmi_walk(ghes_edac_count_dimms, &num_dimm); @@ -425,26 +443,17 @@ int ghes_edac_register(struct ghes *ghes, struct device *dev) layers[0].size = num_dimm; layers[0].is_virt_csrow = true; - /* - * We need to serialize edac_mc_alloc() and edac_mc_add_mc(), - * to avoid duplicated memory controller numbers - */ - mutex_lock(&ghes_edac_lock); - mci = edac_mc_alloc(ghes_edac_mc_num, ARRAY_SIZE(layers), layers, - sizeof(*pvt)); + mci = edac_mc_alloc(1, ARRAY_SIZE(layers), layers, sizeof(struct ghes_edac_pvt)); if (!mci) { pr_info("Can't allocate memory for EDAC data\n"); - mutex_unlock(&ghes_edac_lock); return -ENOMEM; } - pvt = mci->pvt_info; - memset(pvt, 0, sizeof(*pvt)); - list_add_tail(&pvt->list, &ghes_reglist); - pvt->ghes = ghes; - pvt->mci = mci; - mci->pdev = dev; + ghes_pvt = mci->pvt_info; + ghes_pvt->ghes = ghes; + ghes_pvt->mci = mci; + mci->pdev = dev; mci->mtype_cap = MEM_FLAG_EMPTY; mci->edac_ctl_cap = EDAC_FLAG_NONE; mci->edac_cap = EDAC_FLAG_NONE; @@ -452,36 +461,23 @@ int ghes_edac_register(struct ghes *ghes, struct device *dev) mci->ctl_name = "ghes_edac"; mci->dev_name = "ghes"; - if (!ghes_edac_mc_num) { - if (!fake) { - pr_info("This EDAC driver relies on BIOS to enumerate memory and get error reports.\n"); - pr_info("Unfortunately, not all BIOSes reflect the memory layout correctly.\n"); - pr_info("So, the end result of using this driver varies from vendor to vendor.\n"); - pr_info("If you find incorrect reports, please contact your hardware vendor\n"); - pr_info("to correct its BIOS.\n"); - pr_info("This system has %d DIMM sockets.\n", - num_dimm); - } else { - pr_info("This system has a very crappy BIOS: It doesn't even list the DIMMS.\n"); - pr_info("Its SMBIOS info is wrong. It is doubtful that the error report would\n"); - pr_info("work on such system. Use this driver with caution\n"); - } + if (!fake) { + pr_info("This EDAC driver relies on BIOS to enumerate memory and get error reports.\n"); + pr_info("Unfortunately, not all BIOSes reflect the memory layout correctly.\n"); + pr_info("So, the end result of using this driver varies from vendor to vendor.\n"); + pr_info("If you find incorrect reports, please contact your hardware vendor\n"); + pr_info("to correct its BIOS.\n"); + pr_info("This system has %d DIMM sockets.\n", num_dimm); + } else { + pr_info("This system has a very crappy BIOS: It doesn't even list the DIMMS.\n"); + pr_info("Its SMBIOS info is wrong. It is doubtful that the error report would\n"); + pr_info("work on such system. Use this driver with caution\n"); } if (!fake) { - /* - * Fill DIMM info from DMI for the memory controller #0 - * - * Keep it in blank for the other memory controllers, as - * there's no reliable way to properly credit each DIMM to - * the memory controller, as different BIOSes fill the - * DMI bank location fields on different ways - */ - if (!ghes_edac_mc_num) { - dimm_fill.count = 0; - dimm_fill.mci = mci; - dmi_walk(ghes_edac_dmidecode, &dimm_fill); - } + dimm_fill.count = 0; + dimm_fill.mci = mci; + dmi_walk(ghes_edac_dmidecode, &dimm_fill); } else { struct dimm_info *dimm = EDAC_DIMM_PTR(mci->layers, mci->dimms, mci->n_layers, 0, 0, 0); @@ -497,12 +493,8 @@ int ghes_edac_register(struct ghes *ghes, struct device *dev) if (rc < 0) { pr_info("Can't register at EDAC core\n"); edac_mc_free(mci); - mutex_unlock(&ghes_edac_lock); return -ENODEV; } - - ghes_edac_mc_num++; - mutex_unlock(&ghes_edac_lock); return 0; } EXPORT_SYMBOL_GPL(ghes_edac_register); @@ -510,15 +502,9 @@ EXPORT_SYMBOL_GPL(ghes_edac_register); void ghes_edac_unregister(struct ghes *ghes) { struct mem_ctl_info *mci; - struct ghes_edac_pvt *pvt, *tmp; - - list_for_each_entry_safe(pvt, tmp, &ghes_reglist, list) { - if (ghes == pvt->ghes) { - mci = pvt->mci; - edac_mc_del_mc(mci->pdev); - edac_mc_free(mci); - list_del(&pvt->list); - } - } + + mci = ghes_pvt->mci; + edac_mc_del_mc(mci->pdev); + edac_mc_free(mci); } EXPORT_SYMBOL_GPL(ghes_edac_unregister); -- 2.13.0 Regards/Gruss, Boris. Good mailing practices for 400: avoid top-posting and trim the reply.