From: Jeremy Kerr Date: Fri, 11 Jan 2008 13:28:04 +0000 (+0100) Subject: ps3fb: fix deadlock on kexec() X-Git-Tag: v2.6.24-rc8~44 X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=8dab63761219d7bc6a7d7d3b5f0fca76af5533a5;p=linux-2.6-omap-h63xx.git ps3fb: fix deadlock on kexec() Since the introduction of the acquire_console_sem calls in 0333d83509c7d8496c8965b5ba9bc0c98e83c259, kexecing can cause the kernel to deadlock: ps3fb_shutdown() -> unregister_framebuffer() -> fb_notifier_call_chain(FB_EVENT_FB_UNBIND) -> fbcon_fb_unbind() -> unbind_con_driver() -> bind_con_driver() [ acquires console_sem ] -> fbcon_deinit() -> fbops->fb_release(newinfo, 0) -> ps3fb_release() -> ps3fb_sync() [ acquires console_sem ] This change avoids the deadlock by moving the acquire_console_sem() out of ps3fb_sync(), and puts it into the two other callsites, leaving ps3fb_release() to call ps3fb_sync() without the console semaphore. [Geert] - Corrected call sequence above - ps3fb_release() may be called with and without console_sem held. This is an inconsistency that should be fixed at the fb level, but for now, try to acquire console_sem in ps3fb_release(). I think it's safer to let ps3fb_release() try to acquire console_sem and not refresh the screen if it fails, than to call ps3fb_sync() without holding console_sem, as ps3fb_par may be modified at the same time, causing crashes or lockups. Besides, ps3fb_release() only calls ps3fb_sync() to refresh the screen when display flipping is disabled, which is an uncommon case (except during shutdown/kexec). Signed-off-by: Jeremy Kerr Signed-off-by: Geert Uytterhoeven Cc: Benjamin Herrenschmidt Signed-off-by: Linus Torvalds --- diff --git a/drivers/video/ps3fb.c b/drivers/video/ps3fb.c index ae07e02943d..044a423a72c 100644 --- a/drivers/video/ps3fb.c +++ b/drivers/video/ps3fb.c @@ -443,8 +443,6 @@ static int ps3fb_sync(struct fb_info *info, u32 frame) u32 ddr_line_length, xdr_line_length; u64 ddr_base, xdr_base; - acquire_console_sem(); - if (frame > par->num_frames - 1) { dev_dbg(info->device, "%s: invalid frame number (%u)\n", __func__, frame); @@ -464,7 +462,6 @@ static int ps3fb_sync(struct fb_info *info, u32 frame) xdr_line_length); out: - release_console_sem(); return error; } @@ -479,7 +476,10 @@ static int ps3fb_release(struct fb_info *info, int user) if (atomic_dec_and_test(&ps3fb.f_count)) { if (atomic_read(&ps3fb.ext_flip)) { atomic_set(&ps3fb.ext_flip, 0); - ps3fb_sync(info, 0); /* single buffer */ + if (!try_acquire_console_sem()) { + ps3fb_sync(info, 0); /* single buffer */ + release_console_sem(); + } } } return 0; @@ -865,7 +865,9 @@ static int ps3fb_ioctl(struct fb_info *info, unsigned int cmd, break; dev_dbg(info->device, "PS3FB_IOCTL_FSEL:%d\n", val); + acquire_console_sem(); retval = ps3fb_sync(info, val); + release_console_sem(); break; default: @@ -885,7 +887,9 @@ static int ps3fbd(void *arg) set_current_state(TASK_INTERRUPTIBLE); if (ps3fb.is_kicked) { ps3fb.is_kicked = 0; + acquire_console_sem(); ps3fb_sync(info, 0); /* single buffer */ + release_console_sem(); } schedule(); }