Messages in this thread Patch in this message | | | Date | Wed, 15 Jun 2022 10:24:18 +0100 | Subject | Re: [PATCH v2] coresight: configfs: Fix unload of configurations on module exit | From | Suzuki K Poulose <> |
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Cc: configfs folks.
Hi Mike
On 14/06/2022 23:00, Suzuki K Poulose wrote: > Hi Mike, > > Thanks for fixing this. Except for a minor nit, the patch looks good to me.
Spoke too soon. I am able to reproduce the original problem with this patch applied. Here is what I did :
# Load the coresight_etm4x module
$ modprobe coresight_etm4x
# enable autofdo configuration $ echo 1 > /sys/kernel/config/cs-syscfg/configurations/autofdo/enable
# Unload the coresight_etm4x module $ rmmod coresight_etm4x $ lsmod Module Size Used by coresight 77824 0 $ cat /sys/kernel/config/cs-syscfg/configurations/autofdo/enable 1
# Now unload the coresight module, this triggers the splat. $ rmmod coresight
[ 202.455667] cscfg: unloading preloaded configurations [ 202.455689] ======================================================
[ 202.455691] WARNING: possible circular locking dependency detected [ 202.455695] 5.19.0-rc2+ #53 Tainted: G T [ 202.455700] ------------------------------------------------------ [ 202.455702] rmmod/454 is trying to acquire lock: [ 202.455707] ffff00080363f580 (&p->frag_sem){++++}-{4:4}, at: configfs_unregister_group+0x4c/0x190 [ 202.455733] but task is already holding lock: [ 202.455735] ffff8000012e4b98 (cscfg_mutex){+.+.}-{4:4}, at: cscfg_clear_device+0x34/0xfc [coresight] [ 202.455777] which lock already depends on the new lock.
[ 202.455779] the existing dependency chain (in reverse order) is: [ 202.455781] -> #1 (cscfg_mutex){+.+.}-{4:4}: [ 202.455791] lock_acquire+0x68/0x8c [ 202.455801] __mutex_lock+0xa0/0x464 [ 202.455811] mutex_lock_nested+0x44/0x70 [ 202.455819] cscfg_config_sysfs_activate+0x3c/0xec [coresight] [ 202.455846] cscfg_cfg_enable_store+0x84/0xcc [coresight] [ 202.455872] configfs_write_iter+0xd4/0x130 [ 202.455878] new_sync_write+0xdc/0x160 [ 202.455885] vfs_write+0x1c8/0x210 [ 202.455892] ksys_write+0x74/0x100 [ 202.455897] __arm64_sys_write+0x28/0x34 [ 202.455904] invoke_syscall+0x50/0x120 [ 202.455913] el0_svc_common.constprop.0+0x68/0x124 [ 202.455921] do_el0_svc+0x38/0xcc [ 202.455928] el0_svc+0x58/0x100 [ 202.455933] el0t_64_sync_handler+0xf4/0x100 [ 202.455938] el0t_64_sync+0x18c/0x190 [ 202.455944] -> #0 (&p->frag_sem){++++}-{4:4}: [ 202.455954] __lock_acquire+0x11f4/0x1ddc [ 202.455961] lock_acquire.part.0+0xe4/0x220 [ 202.455967] lock_acquire+0x68/0x8c [ 202.455973] down_write+0x78/0x164 [ 202.455980] configfs_unregister_group+0x4c/0x190 [ 202.455985] cscfg_configfs_del_config+0x2c/0x40 [coresight] [ 202.456011] cscfg_unload_owned_cfgs_feats+0x1d0/0x2c0 [coresight] [ 202.456036] cscfg_clear_device+0xec/0xfc [coresight] [ 202.456060] cscfg_exit+0x1c/0x90 [coresight] [ 202.456085] coresight_exit+0x10/0xd80 [coresight] [ 202.456109] __arm64_sys_delete_module+0x19c/0x250 [ 202.456115] invoke_syscall+0x50/0x120 [ 202.456122] el0_svc_common.constprop.0+0x68/0x124 [ 202.456130] do_el0_svc+0x38/0xcc [ 202.456138] el0_svc+0x58/0x100 [ 202.456142] el0t_64_sync_handler+0xf4/0x100 [ 202.456148] el0t_64_sync+0x18c/0x190 [ 202.456152] other info that might help us debug this:
[ 202.456154] Possible unsafe locking scenario:
[ 202.456156] CPU0 CPU1 [ 202.456158] ---- ---- [ 202.456159] lock(cscfg_mutex); [ 202.456164] lock(&p->frag_sem); [ 202.456169] lock(cscfg_mutex); [ 202.456173] lock(&p->frag_sem); [ 202.456177] *** DEADLOCK ***
[ 202.456178] 1 lock held by rmmod/454: [ 202.456183] #0: ffff8000012e4b98 (cscfg_mutex){+.+.}-{4:4}, at: cscfg_clear_device+0x34/0xfc [coresight] [ 202.456219] stack backtrace: [ 202.456222] CPU: 1 PID: 454 Comm: rmmod Tainted: G T 5.19.0-rc2+ #53 [ 202.456230] Hardware name: ARM LTD ARM Juno Development Platform/ARM Juno Development Platform, BIOS EDK II Feb 1 2019 [ 202.456234] Call trace: [ 202.456236] dump_backtrace.part.0+0xd8/0xe4 [ 202.456243] show_stack+0x24/0x80 [ 202.456248] dump_stack_lvl+0x8c/0xb8 [ 202.456257] dump_stack+0x18/0x34 [ 202.456264] print_circular_bug+0x1f8/0x200 [ 202.456271] check_noncircular+0x130/0x144 [ 202.456277] __lock_acquire+0x11f4/0x1ddc [ 202.456284] lock_acquire.part.0+0xe4/0x220 [ 202.456290] lock_acquire+0x68/0x8c [ 202.456295] down_write+0x78/0x164 [ 202.456302] configfs_unregister_group+0x4c/0x190 [ 202.456308] cscfg_configfs_del_config+0x2c/0x40 [coresight] [ 202.456333] cscfg_unload_owned_cfgs_feats+0x1d0/0x2c0 [coresight] [ 202.456357] cscfg_clear_device+0xec/0xfc [coresight] [ 202.456381] cscfg_exit+0x1c/0x90 [coresight] [ 202.456405] coresight_exit+0x10/0xd80 [coresight] [ 202.456429] __arm64_sys_delete_module+0x19c/0x250 [ 202.456435] invoke_syscall+0x50/0x120 [ 202.456442] el0_svc_common.constprop.0+0x68/0x124 [ 202.456450] do_el0_svc+0x38/0xcc [ 202.456458] el0_svc+0x58/0x100 [ 202.456462] el0t_64_sync_handler+0xf4/0x100 [ 202.456468] el0t_64_sync+0x18c/0x190
Suzuki
> > On 06/06/2022 16:26, Mike Leach wrote: >> Any loaded configurations must be correctly unloaded on coresight module >> exit, or issues can arise with nested locking in the configfs directory >> code if built with CONFIG_LOCKDEP. >> >> Prior to this patch, the preloaded configuration configfs directory >> entries >> were being unloaded by the recursive code in >> configfs_unregister_subsystem(). >> >> However, when built with CONFIG_LOCKDEP, this caused a nested lock >> warning, >> which was not mitigated by the LOCKDEP dependent code in >> fs/configfs/dir.c >> designed to prevent this, due to the different directory levels for the >> root of the directory being removed. >> >> As the preloaded (and all other) configurations are registered after >> configfs_register_subsystem(), we now explicitly unload them before the >> call to configfs_unregister_subsystem(). >> >> The new routine cscfg_unload_cfgs_on_exit() iterates through the load >> owner list to unload any remaining configurations that were not unloaded >> by the user before the module exits. This covers both the >> CSCFG_OWNER_PRELOAD and CSCFG_OWNER_MODULE owner types, and will be >> extended to cover future load owner types for CoreSight configurations. >> >> Applies to coresight/next >> >> Fixes: eb2ec49606c2 ("coresight: syscfg: Update load API for config >> loadable modules") >> Reported-by: Suzuki Poulose <suzuki.poulose@arm.com> >> Signed-off-by: Mike Leach <mike.leach@linaro.org> >> --- >> >> Changes since v1: >> Altered ordering of init of cscfg_mgr to ensure lists valid for >> potential exit path on error. >> >> --- >> .../hwtracing/coresight/coresight-syscfg.c | 72 ++++++++++++++++--- >> 1 file changed, 61 insertions(+), 11 deletions(-) >> >> diff --git a/drivers/hwtracing/coresight/coresight-syscfg.c >> b/drivers/hwtracing/coresight/coresight-syscfg.c >> index 11850fd8c3b5..050a32f7e439 100644 >> --- a/drivers/hwtracing/coresight/coresight-syscfg.c >> +++ b/drivers/hwtracing/coresight/coresight-syscfg.c >> @@ -1042,6 +1042,13 @@ static int cscfg_create_device(void) >> if (!cscfg_mgr) >> goto create_dev_exit_unlock; >> + /* initialise the cscfg_mgr structure */ >> + INIT_LIST_HEAD(&cscfg_mgr->csdev_desc_list); >> + INIT_LIST_HEAD(&cscfg_mgr->feat_desc_list); >> + INIT_LIST_HEAD(&cscfg_mgr->config_desc_list); >> + INIT_LIST_HEAD(&cscfg_mgr->load_order_list); >> + atomic_set(&cscfg_mgr->sys_active_cnt, 0); >> + >> /* setup the device */ >> dev = cscfg_device(); >> dev->release = cscfg_dev_release; >> @@ -1056,14 +1063,61 @@ static int cscfg_create_device(void) >> return err; >> } >> -static void cscfg_clear_device(void) >> +/* >> + * Loading and unloading is generally on user discretion. >> + * If exiting due to coresight module unload, we need to unload any >> configurations that remain, >> + * before we unregister the configfs intrastructure. >> + * >> + * Do this by walking the load_owner list and taking appropriate >> action, depending on the load >> + * owner type. >> + * >> + * called with the cscfg_mutex held >> + */ >> + >> +#define LOADABLE_MOD_ERR "cscfg: ERROR - a loadable module failed to >> unload configs on exit\n" > > minor nit: Could we skip this ? > >> + >> +static void cscfg_unload_cfgs_on_exit(void) >> { >> - struct cscfg_config_desc *cfg_desc; >> + struct cscfg_load_owner_info *owner_info = NULL; >> - mutex_lock(&cscfg_mutex); >> - list_for_each_entry(cfg_desc, &cscfg_mgr->config_desc_list, item) { >> - etm_perf_del_symlink_cscfg(cfg_desc); >> + while (!list_empty(&cscfg_mgr->load_order_list)) { >> + >> + /* remove in reverse order of loading */ >> + owner_info = list_last_entry(&cscfg_mgr->load_order_list, >> + struct cscfg_load_owner_info, item); >> + >> + /* action according to type */ >> + switch (owner_info->type) { >> + case CSCFG_OWNER_PRELOAD: >> + /* >> + * preloaded descriptors are statically allocated in >> + * this module - just need to unload dynamic items from >> + * csdev lists, and remove from configfs directories. >> + */ >> + pr_info("cscfg: unloading preloaded configurations\n"); >> + cscfg_unload_owned_cfgs_feats(owner_info); >> + break; >> + >> + case CSCFG_OWNER_MODULE: >> + /* >> + * this is an error - the loadable module must have been >> unloaded prior >> + * to the coresight module unload. Therefore that module >> has not >> + * correctly unloaded configs in its own exit code. >> + * Nothing to do other than emit an error string. >> + */ >> + pr_err(LOADABLE_MOD_ERR); > > Instead : > pr_err("cscfg: ERROR - a loadable module failed" > " to unload configs on exit\n"); > > Otherwise, I can confirm that the patch fixes the reported problem. > >> + break; >> + } >> + >> + /* remove from load order list */ >> + list_del(&owner_info->item); >> } >> +} >> + >> +static void cscfg_clear_device(void) >> +{ >> + mutex_lock(&cscfg_mutex); >> + cscfg_unload_cfgs_on_exit(); >> cscfg_configfs_release(cscfg_mgr); >> device_unregister(cscfg_device()); >> mutex_unlock(&cscfg_mutex); >> @@ -1074,20 +1128,16 @@ int __init cscfg_init(void) >> { >> int err = 0; >> + /* create the device and init cscfg_mgr */ >> err = cscfg_create_device(); >> if (err) >> return err; >> + /* initialise configfs subsystem */ >> err = cscfg_configfs_init(cscfg_mgr); >> if (err) >> goto exit_err; >> - INIT_LIST_HEAD(&cscfg_mgr->csdev_desc_list); >> - INIT_LIST_HEAD(&cscfg_mgr->feat_desc_list); >> - INIT_LIST_HEAD(&cscfg_mgr->config_desc_list); >> - INIT_LIST_HEAD(&cscfg_mgr->load_order_list); >> - atomic_set(&cscfg_mgr->sys_active_cnt, 0); >> - >> /* preload built-in configurations */ >> err = cscfg_preload(THIS_MODULE); >> if (err) >
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