From 57d81f6f393b245894ca0cd828f80ce7e3294f39 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Wed, 1 Jul 2009 09:43:53 +0200 Subject: [PATCH] kmemleak: Fix scheduling-while-atomic bug One of the kmemleak changes caused the following scheduling-while-holding-the-tasklist-lock regression on x86: BUG: sleeping function called from invalid context at mm/kmemleak.c:795 in_atomic(): 1, irqs_disabled(): 0, pid: 1737, name: kmemleak 2 locks held by kmemleak/1737: #0: (scan_mutex){......}, at: [] kmemleak_scan_thread+0x45/0x86 #1: (tasklist_lock){......}, at: [] kmemleak_scan+0x1a9/0x39c Pid: 1737, comm: kmemleak Not tainted 2.6.31-rc1-tip #59266 Call Trace: [] ? __debug_show_held_locks+0x1e/0x20 [] __might_sleep+0x10a/0x111 [] scan_yield+0x17/0x3b [] scan_block+0x39/0xd4 [] kmemleak_scan+0x1bb/0x39c [] ? kmemleak_scan_thread+0x0/0x86 [] kmemleak_scan_thread+0x4a/0x86 [] kthread+0x6e/0x73 [] ? kthread+0x0/0x73 [] kernel_thread_helper+0x7/0x10 kmemleak: 834 new suspected memory leaks (see /sys/kernel/debug/kmemleak) The bit causing it is highly dubious: static void scan_yield(void) { might_sleep(); if (time_is_before_eq_jiffies(next_scan_yield)) { schedule(); next_scan_yield = jiffies + jiffies_scan_yield; } } It called deep inside the codepath and in a conditional way, and that is what crapped up when one of the new scan_block() uses grew a tasklist_lock dependency. This minimal patch removes that yielding stuff and adds the proper cond_resched(). The background scanning thread could probably also be reniced to +10. Signed-off-by: Ingo Molnar Acked-by: Pekka Enberg Signed-off-by: Linus Torvalds --- mm/kmemleak.c | 31 +------------------------------ 1 file changed, 1 insertion(+), 30 deletions(-) diff --git a/mm/kmemleak.c b/mm/kmemleak.c index eeece2deace2..e766e1da09d2 100644 --- a/mm/kmemleak.c +++ b/mm/kmemleak.c @@ -105,7 +105,6 @@ #define MAX_TRACE 16 /* stack trace length */ #define REPORTS_NR 50 /* maximum number of reported leaks */ #define MSECS_MIN_AGE 5000 /* minimum object age for reporting */ -#define MSECS_SCAN_YIELD 10 /* CPU yielding period */ #define SECS_FIRST_SCAN 60 /* delay before the first scan */ #define SECS_SCAN_WAIT 600 /* subsequent auto scanning delay */ @@ -186,10 +185,7 @@ static atomic_t kmemleak_error = ATOMIC_INIT(0); static unsigned long min_addr = ULONG_MAX; static unsigned long max_addr; -/* used for yielding the CPU to other tasks during scanning */ -static unsigned long next_scan_yield; static struct task_struct *scan_thread; -static unsigned long jiffies_scan_yield; /* used to avoid reporting of recently allocated objects */ static unsigned long jiffies_min_age; static unsigned long jiffies_last_scan; @@ -785,21 +781,6 @@ void kmemleak_no_scan(const void *ptr) } EXPORT_SYMBOL(kmemleak_no_scan); -/* - * Yield the CPU so that other tasks get a chance to run. The yielding is - * rate-limited to avoid excessive number of calls to the schedule() function - * during memory scanning. - */ -static void scan_yield(void) -{ - might_sleep(); - - if (time_is_before_eq_jiffies(next_scan_yield)) { - schedule(); - next_scan_yield = jiffies + jiffies_scan_yield; - } -} - /* * Memory scanning is a long process and it needs to be interruptable. This * function checks whether such interrupt condition occured. @@ -840,15 +821,6 @@ static void scan_block(void *_start, void *_end, if (scan_should_stop()) break; - /* - * When scanning a memory block with a corresponding - * kmemleak_object, the CPU yielding is handled in the calling - * code since it holds the object->lock to avoid the block - * freeing. - */ - if (!scanned) - scan_yield(); - object = find_and_get_object(pointer, 1); if (!object) continue; @@ -1014,7 +986,7 @@ static void kmemleak_scan(void) */ object = list_entry(gray_list.next, typeof(*object), gray_list); while (&object->gray_list != &gray_list) { - scan_yield(); + cond_resched(); /* may add new objects to the list */ if (!scan_should_stop()) @@ -1385,7 +1357,6 @@ void __init kmemleak_init(void) int i; unsigned long flags; - jiffies_scan_yield = msecs_to_jiffies(MSECS_SCAN_YIELD); jiffies_min_age = msecs_to_jiffies(MSECS_MIN_AGE); jiffies_scan_wait = msecs_to_jiffies(SECS_SCAN_WAIT * 1000); -- 2.34.1