[PATCH 1/1] utrace: introduce UTRACE_ATTACH_ATOMIC

Add the new UTRACE_ATTACH_ATOMIC flag for utrace_attach_task(). If it is set, UTRACE_ATTACH_CREATE uses GFP_ATOMIC for memory allocations and thus it can be used in atomic context. Suggested-by: Mark Wielaard <mjw(a)redhat.com&gt; Signed-off-by: Oleg Nesterov <oleg(a)redhat.com&gt; --- include/linux/utrace.h | 1 + kernel/utrace.c | 12 ++++++++---- 2 files changed, 9 insertions(+), 4 deletions(-) diff --git a/include/linux/utrace.h b/include/linux/utrace.h index f37373b..46959af 100644 --- a/include/linux/utrace.h +++ b/include/linux/utrace.h @@ -317,6 +317,7 @@ static inline enum utrace_syscall_action utrace_syscall_action(u32 action) #define UTRACE_ATTACH_MATCH_MASK 0x000f #define UTRACE_ATTACH_CREATE 0x0010 /* Attach a new engine. */ #define UTRACE_ATTACH_EXCLUSIVE 0x0020 /* Refuse if existing match. */ +#define UTRACE_ATTACH_ATOMIC 0x0040 /* For _CREATE, don't sleep */ /** * struct utrace_engine - per-engine structure diff --git a/kernel/utrace.c b/kernel/utrace.c index c817a46..a169e1b 100644 --- a/kernel/utrace.c +++ b/kernel/utrace.c @@ -113,9 +113,9 @@ void task_utrace_unlock(struct task_struct *task) * * This returns false only in case of a memory allocation failure. */ -static bool utrace_task_alloc(struct task_struct *task) +static bool utrace_task_alloc(struct task_struct *task, gfp_t gfp_flags) { - struct utrace *utrace = kmem_cache_zalloc(utrace_cachep, GFP_KERNEL); + struct utrace *utrace = kmem_cache_zalloc(utrace_cachep, gfp_flags); if (unlikely(!utrace)) return false; spin_lock_init(&utrace->lock); @@ -295,6 +295,7 @@ struct utrace_engine *utrace_attach_task( { struct utrace *utrace = task_utrace_struct(target); struct utrace_engine *engine; + gfp_t gfp_flags; int ret; if (!(flags & UTRACE_ATTACH_CREATE)) { @@ -317,13 +318,16 @@ struct utrace_engine *utrace_attach_task( */ return ERR_PTR(-EPERM); + gfp_flags = (flags & UTRACE_ATTACH_ATOMIC) + ? GFP_ATOMIC : GFP_KERNEL; + if (!utrace) { - if (unlikely(!utrace_task_alloc(target))) + if (unlikely(!utrace_task_alloc(target, gfp_flags))) return ERR_PTR(-ENOMEM); utrace = task_utrace_struct(target); } - engine = kmem_cache_alloc(utrace_engine_cachep, GFP_KERNEL); + engine = kmem_cache_alloc(utrace_engine_cachep, gfp_flags); if (unlikely(!engine)) return ERR_PTR(-ENOMEM); -- 1.5.5.1