From 67cb85fdcee7fbc61c09c00360d1a4ae37641db4 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Wed, 12 Apr 2017 22:07:29 +0200 Subject: [PATCH] ia64/salinfo: Replace racy task affinity logic Some of the file operations in /proc/sal require to run code on the requested cpu. This is achieved by temporarily setting the affinity of the calling user space thread to the requested CPU and reset it to the original affinity afterwards. That's racy vs. CPU hotplug and concurrent affinity settings for that thread resulting in code executing on the wrong CPU and overwriting the new affinity setting. Replace it by using work_on_cpu_safe() which guarantees to run the code on the requested CPU or to fail in case the CPU is offline. Signed-off-by: Thomas Gleixner Cc: Fenghua Yu Cc: Tony Luck Cc: linux-ia64@vger.kernel.org Cc: Herbert Xu Cc: "Rafael J. Wysocki" Cc: Peter Zijlstra Cc: Benjamin Herrenschmidt Cc: Sebastian Siewior Cc: Lai Jiangshan Cc: Viresh Kumar Cc: Michael Ellerman Cc: Tejun Heo Cc: "David S. Miller" Cc: Len Brown Link: http://lkml.kernel.org/r/20170412201042.341863457@linutronix.de Signed-off-by: Thomas Gleixner --- arch/ia64/kernel/salinfo.c | 31 ++++++++++++------------------- 1 file changed, 12 insertions(+), 19 deletions(-) diff --git a/arch/ia64/kernel/salinfo.c b/arch/ia64/kernel/salinfo.c index d194d5c83d32..63dc9cdc95c5 100644 --- a/arch/ia64/kernel/salinfo.c +++ b/arch/ia64/kernel/salinfo.c @@ -179,14 +179,14 @@ struct salinfo_platform_oemdata_parms { const u8 *efi_guid; u8 **oemdata; u64 *oemdata_size; - int ret; }; -static void +static long salinfo_platform_oemdata_cpu(void *context) { struct salinfo_platform_oemdata_parms *parms = context; - parms->ret = salinfo_platform_oemdata(parms->efi_guid, parms->oemdata, parms->oemdata_size); + + return salinfo_platform_oemdata(parms->efi_guid, parms->oemdata, parms->oemdata_size); } static void @@ -380,16 +380,7 @@ salinfo_log_release(struct inode *inode, struct file *file) return 0; } -static void -call_on_cpu(int cpu, void (*fn)(void *), void *arg) -{ - cpumask_t save_cpus_allowed = current->cpus_allowed; - set_cpus_allowed_ptr(current, cpumask_of(cpu)); - (*fn)(arg); - set_cpus_allowed_ptr(current, &save_cpus_allowed); -} - -static void +static long salinfo_log_read_cpu(void *context) { struct salinfo_data *data = context; @@ -399,6 +390,7 @@ salinfo_log_read_cpu(void *context) /* Clear corrected errors as they are read from SAL */ if (rh->severity == sal_log_severity_corrected) ia64_sal_clear_state_info(data->type); + return 0; } static void @@ -430,7 +422,7 @@ retry: spin_unlock_irqrestore(&data_saved_lock, flags); if (!data->saved_num) - call_on_cpu(cpu, salinfo_log_read_cpu, data); + work_on_cpu_safe(cpu, salinfo_log_read_cpu, data); if (!data->log_size) { data->state = STATE_NO_DATA; cpumask_clear_cpu(cpu, &data->cpu_event); @@ -459,11 +451,13 @@ salinfo_log_read(struct file *file, char __user *buffer, size_t count, loff_t *p return simple_read_from_buffer(buffer, count, ppos, buf, bufsize); } -static void +static long salinfo_log_clear_cpu(void *context) { struct salinfo_data *data = context; + ia64_sal_clear_state_info(data->type); + return 0; } static int @@ -486,7 +480,7 @@ salinfo_log_clear(struct salinfo_data *data, int cpu) rh = (sal_log_record_header_t *)(data->log_buffer); /* Corrected errors have already been cleared from SAL */ if (rh->severity != sal_log_severity_corrected) - call_on_cpu(cpu, salinfo_log_clear_cpu, data); + work_on_cpu_safe(cpu, salinfo_log_clear_cpu, data); /* clearing a record may make a new record visible */ salinfo_log_new_read(cpu, data); if (data->state == STATE_LOG_RECORD) { @@ -531,9 +525,8 @@ salinfo_log_write(struct file *file, const char __user *buffer, size_t count, lo .oemdata = &data->oemdata, .oemdata_size = &data->oemdata_size }; - call_on_cpu(cpu, salinfo_platform_oemdata_cpu, &parms); - if (parms.ret) - count = parms.ret; + count = work_on_cpu_safe(cpu, salinfo_platform_oemdata_cpu, + &parms); } else data->oemdata_size = 0; } else -- 2.20.1